a(n) = binomial(2n,n) - n; number of (weakly) increasing or decreasing maps from 1,...,n to 1,...,n.

A045992

a(n) = binomial(2n,n) - n; number of (weakly) increasing or decreasing maps from 1,...,n to 1,...,n.

Terms

    a(0) =1a(1) =1a(2) =4a(3) =17a(4) =66a(5) =247a(6) =918a(7) =3425a(8) =12862a(9) =48611a(10) =184746a(11) =705421a(12) =2704144a(13) =10400587a(14) =40116586a(15) =155117505a(16) =601080374a(17) =2333606203a(18) =9075135282a(19) =35345263781a(20) =137846528800a(21) =538257874419

External references