Edit : Let $X_p$ be the set of isometry classes of 4-dimensional positive definite lattices satisfying the property $L^\sharp/L\simeq (\mathbf Z/p)^2$. The set $X_n$ is stable under the involution $\tau : L\mapsto pL^\sharp$.
The question seems to ask whether or not $X_p^\tau$ is non-empty. Will Jagy has given evidences for a positive answer. Nevertheless, one might ask whether the same holds when one restricts the question to a given genus (enera are also stable under $tau$).
Here are some heuristics :
Let $p$ be a prime, congruent to $3$ mod $4$. Then there is such a genus on the $\mathbf Q$-quadratic space $[1,1,p,p]$. Here is the number of fixed (resp exchanged) lattices are as follows
p= 3 fix= 1 move= 0 proportion= 1.00
p= 7 fix= 1 move= 0 proportion= 1.00
p= 11 fix= 3 move= 0 proportion= 1.00
p= 19 fix= 3 move= 0 proportion= 1.00
p= 23 fix= 6 move= 0 proportion= 1.00
p= 31 fix= 6 move= 0 proportion= 1.00
p= 43 fix= 5 move= 2 proportion= 0.714
p= 47 fix= 15 move= 0 proportion= 1.00
p= 59 fix= 21 move= 0 proportion= 1.00
p= 67 fix= 7 move= 6 proportion= 0.538
p= 71 fix= 28 move= 0 proportion= 1.00
p= 79 fix= 20 move= 2 proportion= 0.909
p= 83 fix= 27 move= 2 proportion= 0.931
p= 103 fix= 25 move= 6 proportion= 0.807
p= 107 fix= 33 move= 6 proportion= 0.846
p= 127 fix= 30 move= 12 proportion= 0.714
p= 131 fix= 65 move= 2 proportion= 0.970
p= 139 fix= 39 move= 12 proportion= 0.765
p= 151 fix= 49 move= 12 proportion= 0.804
p= 163 fix= 15 move= 42 proportion= 0.263
p= 167 fix= 88 move= 6 proportion= 0.937
p= 179 fix= 85 move= 12 proportion= 0.876
p= 191 fix= 117 move= 6 proportion= 0.951
p= 199 fix= 81 move= 20 proportion= 0.802
p= 211 fix= 57 move= 42 proportion= 0.576
p= 223 fix= 70 move= 42 proportion= 0.625
p= 227 fix= 105 move= 30 proportion= 0.777
p= 239 fix= 165 move= 12 proportion= 0.933
p= 251 fix= 161 move= 20 proportion= 0.890
p= 263 fix= 156 move= 30 proportion= 0.839
p= 271 fix= 132 move= 42 proportion= 0.759
p= 283 fix= 75 move= 90 proportion= 0.455
p= 307 fix= 81 move= 110 proportion= 0.424
p= 311 fix= 266 move= 20 proportion= 0.930
p= 331 fix= 87 move= 132 proportion= 0.397
p= 347 fix= 155 move= 110 proportion= 0.585
p= 359 fix= 304 move= 42 proportion= 0.879
p= 367 fix= 144 move= 132 proportion= 0.521
p= 379 fix= 99 move= 182 proportion= 0.353
p= 383 fix= 289 move= 72 proportion= 0.801
p= 419 fix= 333 move= 90 proportion= 0.787
p= 431 fix= 399 move= 72 proportion= 0.847
p= 439 fix= 285 move= 132 proportion= 0.684
p= 443 fix= 195 move= 210 proportion= 0.481
p= 463 fix= 140 move= 272 proportion= 0.340
p= 467 fix= 287 move= 182 proportion= 0.612
p= 479 fix= 525 move= 72 proportion= 0.880
p= 487 fix= 147 move= 306 proportion= 0.325
p= 491 fix= 387 move= 156 proportion= 0.713
p= 499 fix= 129 move= 342 proportion= 0.274
Similarly, in the following cases, there exist such a genus on $A_2\perp p.A_2$:
p= 5 fix= 1 move= 0 proportion= 1.00
p= 11 fix= 3 move= 0 proportion= 1.00
p= 17 fix= 3 move= 0 proportion= 1.00
p= 23 fix= 6 move= 0 proportion= 1.00
p= 29 fix= 6 move= 0 proportion= 1.00
p= 41 fix= 10 move= 0 proportion= 1.00
p= 47 fix= 15 move= 0 proportion= 1.00
p= 53 fix= 9 move= 2 proportion= 0.818
p= 59 fix= 21 move= 0 proportion= 1.00
p= 71 fix= 28 move= 0 proportion= 1.00
p= 83 fix= 27 move= 2 proportion= 0.931
p= 89 fix= 27 move= 2 proportion= 0.931
p= 101 fix= 35 move= 2 proportion= 0.946
p= 107 fix= 33 move= 6 proportion= 0.846
p= 113 fix= 22 move= 12 proportion= 0.647
p= 131 fix= 65 move= 2 proportion= 0.970
p= 137 fix= 26 move= 20 proportion= 0.565
p= 149 fix= 49 move= 12 proportion= 0.804
p= 167 fix= 88 move= 6 proportion= 0.937
p= 173 fix= 56 move= 20 proportion= 0.737
p= 179 fix= 85 move= 12 proportion= 0.876
p= 191 fix= 117 move= 6 proportion= 0.951
p= 197 fix= 45 move= 42 proportion= 0.518
p= 227 fix= 105 move= 30 proportion= 0.777
p= 233 fix= 63 move= 56 proportion= 0.529
p= 239 fix= 165 move= 12 proportion= 0.933
p= 251 fix= 161 move= 20 proportion= 0.890
p= 257 fix= 92 move= 56 proportion= 0.622
p= 263 fix= 156 move= 30 proportion= 0.839
p= 269 fix= 132 move= 42 proportion= 0.759
p= 281 fix= 125 move= 56 proportion= 0.690
p= 293 fix= 117 move= 72 proportion= 0.619
Studying these repartitions seems to be quite interesting.
Original post :
The answer is no : if you run the following Magma code :
M:=Matrix(Integers(),4,4,[1,0,1,1,0,2,1,2,0,0,5,1,0,0,0,10]);
M:=M+Transpose(M);
L:=LatticeWithGram(M);
H:=GenusRepresentatives(L);
for h in H do
print "h= lattice with Gram", GramMatrix(h);
hd:=DualBasisLattice(h);
MD:=37*LLLGram(GramMatrix(hd));
print "rescaled dual = lattice with Gram", MD;
a,b:=IsIsometric(h,LatticeWithGram(MD));
print "are isometric : ", a;
print " ";
end for;
on the [online calculator][1], you obtain the following result :
h= lattice with Gram
[ 2 0 1 1]
[ 0 4 1 2]
[ 1 1 10 1]
[ 1 2 1 20]
rescaled dual = lattice with Gram
[ 2 0 -1 -1]
[ 0 4 -1 -2]
[-1 -1 10 1]
[-1 -2 1 20]
are isometric : true
h= lattice with Gram
[ 4 -1 2 1]
[-1 4 -1 0]
[ 2 -1 6 -2]
[ 1 0 -2 20]
rescaled dual = lattice with Gram
[ 2 1 -1 0]
[ 1 8 -4 1]
[-1 -4 12 2]
[ 0 1 2 10]
are isometric : false
h= lattice with Gram
[ 4 1 1 1]
[ 1 6 3 1]
[ 1 3 8 -1]
[ 1 1 -1 10]
rescaled dual = lattice with Gram
[ 4 1 -1 -1]
[ 1 6 -3 -1]
[-1 -3 8 -1]
[-1 -1 -1 10]
are isometric : true
h= lattice with Gram
[ 2 1 0 -1]
[ 1 8 -1 -4]
[ 0 -1 10 -2]
[-1 -4 -2 12]
rescaled dual = lattice with Gram
[ 4 1 1 0]
[ 1 4 2 1]
[ 1 2 6 -2]
[ 0 1 -2 20]
are isometric : false
[1]: http://magma.maths.usyd.edu.au/calc/