A185183 G.f. A(x) satisfies A(x) = 1+x + x^2*[d/dx A(x)^2].
1, 1, 2, 10, 72, 672, 7640, 102072, 1564864, 27064448, 521248320, 11064781760, 256702399360, 6462978471168, 175520877380992, 5115062135795584, 159227683153536000, 5273353734210310144, 185143079148664099840, 6869062513111759635456
Offset: 0
Keywords
Examples
G.f.: A(x) = 1 + x + 2*x^2 + 10*x^3 + 72*x^4 + 672*x^5 + 7640*x^6 +... Related series: A(x)^2 = 1 + 2*x + 5*x^2 + 24*x^3 + 168*x^4 + 1528*x^5 + 17012*x^6 +... d/dx A(x)^2 = 2 + 10*x + 72*x^2 + 672*x^3 + 7640*x^4 + 102072*x^5 +...
Links
- Vaclav Kotesovec, Table of n, a(n) for n = 0..400
Programs
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PARI
{a(n)=local(A=1+x); for(i=1, n, A=1+x+x^2*deriv(A^2+x*O(x^n))); polcoeff(A, n)} for(n=0,30,print1(a(n),", "))
Formula
G.f. A(x) satisfies: A(x) = 1+x + 2*x^2*A(x)*A'(x).
a(n) ~ c * n! * 2^n / sqrt(n), where c = 0.493602095524198015213766719826126125048... - Vaclav Kotesovec, Feb 21 2014
a(0) = a(1) = 1; a(n) = (n-1) * Sum_{k=0..n-1} a(k) * a(n-k-1). - Ilya Gutkovskiy, Jul 05 2020
a(0) = a(1) = 1; a(n) = 2 * Sum_{k=0..n-1} k * a(k) * a(n-1-k). - Seiichi Manyama, Jul 16 2025