A333934 Number of permutations of [n] such that the product of the first k elements and the product of the last k elements are multiples of k for all k in [n].

1, 1, 2, 2, 8, 8, 132, 272, 1844, 7824, 219392, 879040, 9865488, 30363264, 1348905760, 26759363296, 265338415104, 1871331759456, 24675601835904, 166652846570112, 1969110048305664, 22090834149738048, 2586719545294006272, 22961806952814951168, 289429435718440962048

Offset

0,3

Links

Table of n, a(n) for n=0..24.

Wikipedia, Permutation

Example

a(5) = 8: 12345, 14325, 14352, 21345, 25341, 52341, 54312, 54321.

Crossrefs

Cf. A333711, A333892.

Sequence in context: A066988 A100384 A000023 * A244676 A010584 A131659

Adjacent sequences: A333931 A333932 A333933 * A333935 A333936 A333937

Keyword

nonn

Author

Alois P. Heinz, Apr 10 2020

Status

approved