[seqfan] Langford sequences

[William Marshall]

The OEIS lists A014552(27) = 111683606778027803456, calculated by a 
group headed by Krajecki, but this is now in doubt as a second group led 
by Bar-Noy calculated a(27) as 111683611098764903232 in July last year. 
(This also puts the value of A176127(27) listed on the OEIS in doubt.)

Therefore someone needs to verify which of these values (if either) is 
correct.

The Bar-Noy group also claims that a(28) = 1607383260609382393152, but 
this still appears to be unverified too.

Bar-Noy also claims new values for the Nickerson variant (A059106), with 
a(24) = 102388058845620672 and a(25) = 1317281759888482688.

Their paper is available at http://arxiv.org/abs/1507.00315.

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