You answered your question yourself: it is published on the web site that you refer to. The author of the web site cites his sources, in most cases these are personal communications. Many results of this sort are spread by correspondence, on Internet, and by oral personal communication. There is also a journal "Experimental Mathematics" which publishes these kinds of observations, even those for which the author has no explanation.
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Added link to the journal to make the answer better referenced + Minor typo fixed
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