A001418 Number of ways of folding an n X n sheet of stamps. (Formerly M4587 N1956)

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

Offset

1,2

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

Table of n, a(n) for n=1..7.

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.

Example

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.

Crossrefs

Cf. A000136, A000560, A001417, A195646.

Sequence in context: A286315 A270112 A281127 * A123268 A088080 A230472

Adjacent sequences: A001415 A001416 A001417 * A001419 A001420 A001421

Keyword

nonn,hard,more

Author

N. J. A. Sloane

Extensions

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

Offset corrected by Anders Kaseorg, Nov 29 2024

Status

approved