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A225963
Number of permutations of [n] having exactly 2 strong fixed blocks.
2
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
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
KEYWORD
nonn
AUTHOR
Alois P. Heinz, May 22 2013
STATUS
approved