A268869 Number of sequences in {1,...,n}^n with longest increasing subsequence of length two.

1, 16, 175, 1771, 17906, 184920, 1958979, 21253375, 235401166, 2653427140, 30356604642, 351714783980, 4119532070980, 48708027030608, 580682498991627, 6973355148949335, 84286653134676230, 1024694093358751200, 12522664845237058050, 153762682169941498170

Offset

2,2

Links

Alois P. Heinz, Table of n, a(n) for n = 2..900

Formula

a(n) = A239295(n) - A088218(n) = A239295(n) - A001700(n-1).

Example

a(2) = 1: 12.
a(3) = 16: 112, 113, 121, 122, 131, 132, 133, 212, 213, 223, 231, 232, 233, 312, 313, 323.
a(4) = 175: 1112, 1113, 1114, 1121, ..., 4414, 4423, 4424, 4434.

Crossrefs

Column k=2 of A245667.

Cf. A001700, A088218, A239295.

Sequence in context: A187720 A017931 A021129 * A268459 A070030 A283278

Adjacent sequences: A268866 A268867 A268868 * A268870 A268871 A268872

Keyword

nonn,easy

Author

Alois P. Heinz, Feb 15 2016

Status

approved