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Number of ways of folding a 2 X n strip of stamps.
(Formerly M1891 N0745)
0

%I M1891 N0745 #44 Feb 01 2022 23:56:37

%S 1,2,8,60,320,1980,10512,60788,320896,1787904,9381840,51081844,

%T 266680992,1429703548,7432424160,39409195740,204150606976,

%U 1073644675448,5545305620064

%N Number of ways of folding a 2 X n strip of stamps.

%C a(n), called G(n,2), is known to be divisible by 4n for n >= 2. - _Fred Lunnon_, Dec 08 2013

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H R. Dickau, <a href="http://robertdickau.com/mapfolding.html">Map Folding</a>

%H R. Dickau, <a href="http://demonstrations.wolfram.com/FoldingA2NSheetOfLabeledStamps/">Folding a 2xn Sheet of Labeled Stamps</a>, Wolfram Demonstrations Project

%H W. F. Lunnon, <a href="http://dx.doi.org/10.1093/comjnl/14.1.75">Multi-dimensional map-folding</a>, Computer Journal 14 1971 75-80.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/MapFolding.html">Map Folding</a>

%H <a href="/index/Fo#fold">Index entries for sequences obtained by enumerating foldings</a>

%K nonn,more

%O 0,2

%A _N. J. A. Sloane_

%E a(12)-a(18) from _Fred Lunnon_, Dec 08 2013