A001416 Number of ways of folding a 3 X n strip of stamps.

1, 6, 60, 1368, 15552, 201240, 2016432, 21582624, 201060768, 1944012744, 17257455960, 156760071600, 1346073913440, 11734199738820, 98420246759688

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• hard
• more

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, Stamp Folding, 2010.
• Hunter Hogan, mapFolding: A computational framework for enumerating distinct folding patterns of rectangular maps, GitHub repository, (2025).
• W. F. Lunnon, Multi-dimensional map-folding, The Computer Journal, Volume 14, Issue 1, 1971, Pages 75-80.
• Eric Weisstein's World of Mathematics, Map Folding.
• Index entries for sequences obtained by enumerating foldings

Crossrefs

Cf. A000136, A000560, A001415, A001417, A001418, A195646.

Extensions

a(8)-a(14) from Fred Lunnon and Sean A. Irvine, Dec 26 2017