[seqfan] A005646 now extended to 12 terms.

Robert Munafo mrob27 at gmail.com
Mon Jan 11 05:06:02 CET 2010

After about 4.5 days of calculation I can now report A005646(12)=184321511.
More details on the web page at http://mrob.com/pub/math/seq-a005646.html

Given that the sequence already has proven links to A000055 and to A039754,
A034189/A034190 and related sequences, with graph theory interpretations, it
seems likely that further insight is possible.

The subdiagonal of the "triangle" seems particularly promising: 0, 0, 1, 3,
17, 74, 358, 1631, 7563, 34751, 160807, ... (this will be A171875, when we
have a chance to submit new work to the OEIS)

 Robert Munafo  --  mrob.com

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