A152496 1/3 of the number of permutations of 2 indistinguishable copies of 1..n with exactly 4 local maxima.

0, 0, 0, 113, 16565, 1216902, 65819156, 3026987243, 126794945523, 5020186173560, 191940972943658, 7179017518306893, 264789361664356313, 9680016979445645738, 351879352694331441600, 12745281650338440074831, 460591166578400672643359, 16621008007245773574764028

Offset

1,4

Links

Andrew Howroyd, Table of n, a(n) for n = 1..200

Formula

a(n) = A334774(n,4)/3. - Andrew Howroyd, May 12 2020

Prog

(PARI) \\ PeaksBySig defined in A334774.
a(n)={PeaksBySig(vector(n, i, 2), [3])[1]/3} \\ Andrew Howroyd, May 12 2020

Crossrefs

Cf. A334774.

Sequence in context: A218371 A218637 A218241 * A176825 A187703 A352400

Adjacent sequences: A152493 A152494 A152495 * A152497 A152498 A152499

Keyword

nonn

Author

R. H. Hardin, Dec 06 2008

Extensions

Terms a(11) and beyond from Andrew Howroyd, May 11 2020

Status

approved