A225963 Number of permutations of [n] having exactly 2 strong fixed blocks.

1, 5, 25, 134, 815, 5657, 44549, 394266, 3883182, 42174500, 500942458, 6460077110, 89875729761, 1341559805867, 21382747361727, 362402701510514, 6507348542427217, 123394642353693319, 2463866954996239829, 51670868533003154264, 1135456889195715187948

Offset

4,2

Comments

See A186373 for the definition of strong fixed blocks.

Links

Alois P. Heinz, Table of n, a(n) for n = 4..450

Formula

a(n) ~ n! / n^2. - Vaclav Kotesovec, Aug 29 2014

Crossrefs

Column k=2 of A186373.

Sequence in context: A355839 A344396 A351587 * A222570 A344268 A144818

Adjacent sequences: A225960 A225961 A225962 * A225964 A225965 A225966

Keyword

nonn

Author

Alois P. Heinz, May 22 2013

Status

approved