A351879 a(0) = a(1) = 1; a(n) = -Sum_{k=0..n-2} binomial(n-2,k) * a(k) * a(n-k-2).

1, 1, -1, -2, 0, 10, 10, -60, -220, 400, 4200, 2200, -90200, -290400, 1892000, 15796000, -24024000, -775676000, -1592492000, 36509880000, 240055640000, -1435950560000, -23703057840000, 7376731120000, 2082346354000000, 9478853472000000, -162472029808000000

Offset

0,4

Links

Table of n, a(n) for n=0..26.

Formula

E.g.f. A(x) satisfies: A(x) = 1 + x - Integral( Integral A(x)^2 dx) dx.

Mathematica

a[0] = a[1] = 1; a[n_] := a[n] = -Sum[Binomial[n - 2, k] a[k] a[n - k - 2], {k, 0, n - 2}]; Table[a[n], {n, 0, 26}]

Crossrefs

Cf. A007558, A307374, A346078.

Sequence in context: A371551 A334615 A303350 * A070681 A228539 A061189

Adjacent sequences: A351876 A351877 A351878 * A351880 A351881 A351882

Keyword

sign

Author

Ilya Gutkovskiy, Feb 23 2022

Status

approved