A007975 Number of permutations that are 3 "block reversals" away from 12...n.

2, 55, 389, 1563, 4642, 11407, 24600, 48204, 87758, 150707, 246787, 388445, 591294, 874603, 1261822, 1781142, 2466090, 3356159, 4497473, 5943487, 7755722, 10004535, 12769924, 16142368, 20223702, 25128027, 30982655, 37929089, 46124038, 55740467, 66968682, 80017450, 95115154, 112510983, 132476157, 155305187, 181317170

Offset

4,1

Links

Table of n, a(n) for n=4..40.

Formula

a(n) = A228397(n) - A228396(n). See C. Homberger links from A228396. - Martin Fuller, Mar 31 2025

Crossrefs

Cf. A007972, A007973, A007974.

Cf. A000124, A228396, A228397.

Column k=3 of A300003.

Sequence in context: A356985 A280209 A157262 * A109796 A186886 A024029

Adjacent sequences: A007972 A007973 A007974 * A007976 A007977 A007978

Keyword

nonn

Author

J. H. Conway

Extensions

More terms from Sean A. Irvine, Feb 22 2018

a(34) onwards from Martin Fuller, Mar 31 2025

Status

approved