A001415 Number of ways of folding a 2 X n strip of stamps.

1, 2, 8, 60, 320, 1980, 10512, 60788, 320896, 1787904, 9381840, 51081844, 266680992, 1429703548, 7432424160, 39409195740, 204150606976, 1073644675448, 5545305620064, 28980175671212, 149302889205120

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• more

Comments

a(n), called G(n,2), is known to be divisible by 4n for n >= 2. - Fred Lunnon, Dec 08 2013

References

• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Robert Dickau, Map Folding
• Robert Dickau, Folding a 2xn Sheet of Labeled Stamps, Wolfram Demonstrations Project
• Hunter Hogan, mapFolding: A computational framework for enumerating distinct folding patterns of rectangular maps, GitHub repository, (2025).
• W. F. Lunnon, Multi-dimensional map-folding, Computer Journal 14 1971 75-80.
• Eric Weisstein's World of Mathematics, Map Folding
• Index entries for sequences obtained by enumerating foldings

Extensions

a(12)-a(18) from Fred Lunnon, Dec 08 2013

a(19)-a(20) from Hunter Hogan, Mar 21 2025