A001418 Number of ways of folding an n X n sheet of stamps.

1, 8, 1368, 300608, 186086600, 123912532224, 129950723279272

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• hard
• more

Examples

			For n = 2 the a(2) = 8 foldings of a sheet labeled 1234 in reading order are 1243, 1342, 2134, 2431, 3124, 3421, 4213, 4312.
		

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

• 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.

Crossrefs

Cf. A000136, A000560, A001417, A195646.

Extensions

a(6)-a(7) from Sean A. Irvine, Jan 11 2018

Offset corrected by Anders Kaseorg, Nov 29 2024