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%I #17 Aug 12 2015 23:41:20
%S 32,26,444,1628,5906,80,126960,380882,2097152,1047588,148814,8951040,
%T 5406720,242,127842440,11419626400,12885001946,160159528116,
%U 687195466408,6390911336402,11728121233408,20104735604736
%N Period of the first difference of Ulam 1-additive sequence U(2,2n+1).
%C It was proved by Akeran that a(2^k-1) = 3^(k+1) - 1.
%C Note that a(n)=2^(2n+1) as soon as A100730(n)=2^(2n+3)-2, that happens for n=(m-2)/2 with m>=6 being an even element of A073639.
%H Max Alekseyev, <a href="/A100729/b100729.txt">Table of n, a(n) for n = 2..31</a>
%H M. Akeran, <a href="/A003668/a003668.pdf">On some 1-additive sequences</a>
%H J. Cassaigne and S. R. Finch, <a href="http://www.emis.de/journals/EM/expmath/volumes/4/4.html">A class of 1-additive sequences and additive recurrences</a>
%H S. R. Finch, <a href="http://www.emis.de/journals/EM/expmath/volumes/1/1.html">Patterns in 1-additive sequences</a>, Experimental Mathematics 1 (1992), 57-63.
%e For k=2, we have a(3)=3^3-1=26.
%Y Cf. A100730 for the fundamental difference, A001857 for U(2, 3), A007300 for U(2, 5), A003668 for U(2, 7).
%Y Cf. also A006844.
%K nonn
%O 2,1
%A _Ralf Stephan_, Dec 03 2004
%E a(3) corrected from 25 to 26 by _Hugo van der Sanden_ and Bertram Felgenhauer (int-e(AT)gmx.de), Nov 11 2007
%E More terms from Balakrishnan V (balaji.iitm1(AT)gmail.com), Nov 15 2007
%E a(21..31) and b-file from _Max Alekseyev_, Dec 01 2007
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