Timeline for Integer strings such as: 4,1,1,3,4,2,3,2
Current License: CC BY-SA 3.0
3 events
| when toggle format | what | by | license | comment | |
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| Oct 16, 2016 at 9:16 | comment | added | shreevatsa | Indeed it's present in Knuth: the very first paragraph of Volume 4A mentions this ("Langford pairs") as an example of combinatorics, and already on page 2 he points out they exist only when when $n = 4m - 1$ or $n = 4m$, and that the number of essentially different pairings $L_n$ "might be roughly of order $(4n/e^3)^{n+1/2}$ when it is nonzero (see exercise 5); and in fact this prediction turns out to be basically correct in all known cases." (His $L_n$ numbers are smaller than the OPs, presumably because of differing definitions of "essentially different".) | |
| Aug 11, 2011 at 7:31 | comment | added | Gerhard Paseman | Welcome back to MathOverflow! Gerhard "Apologies For Missing You Before" Paseman, 2011.08.11 | |
| Aug 11, 2011 at 7:20 | history | answered | Brendan McKay | CC BY-SA 3.0 |