A180880 Number of permutations p() of 1..n+3 with centered difference p(i+1)-p(i-1) < 0 exactly twice.

6, 50, 360, 1960, 10010, 45738, 203616, 854700, 3560172, 14299428, 57595824, 226022940, 895687650, 3473777450, 13672916400, 52745436172, 207268333844, 798176908620, 3139574496240, 12092845015888, 47667323303236

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n=1..100

Prog

(bc) /* See A180887 */

Crossrefs

Column 3 of A180887.

Sequence in context: A241781 A272469 A223816 * A308860 A318162 A027330

Adjacent sequences: A180877 A180878 A180879 * A180881 A180882 A180883

Keyword

nonn

Author

R. H. Hardin, Sep 23 2010

Status

approved