a(1) = 1, a(2) = 1, a(n+1) = 2n*a(n) - a(n-1). Symmetrically a(n) = (a(n-1) + a(n+1))/((n-1) + (n+1)).

A093986

a(1) = 1, a(2) = 1, a(n+1) = 2n*a(n) - a(n-1). Symmetrically a(n) = (a(n-1) + a(n+1))/((n-1) + (n+1)).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =17a(4) =133a(5) =1313a(6) =15623a(7) =217409a(8) =3462921a(9) =62115169a(10) =1238840459a(11) =27192374929a(12) =651378157837

External references