A215125 E.g.f.: Sum_{n>=0} d^n/dx^n (x + x^2)^(2*n) / (2*n)!.

1, 1, 7, 33, 223, 1753, 14391, 137137, 1382383, 14981673, 174494983, 2135204161, 27643067007, 375548195833, 5326762882903, 78889684038993, 1213984929832591, 19377034523034697, 320293617185965863, 5468629894127442913, 96328047496084810783, 1747805367475759936281

Offset

0,3

Comments

Compare to the identity:

exp(x) = Sum_{n>=0} d^n/dx^n x^(2*n) / (2*n)!.

Links

Table of n, a(n) for n=0..21.

Example

E.g.f.: A(x) = 1 + x + 7*x^2/2! + 33*x^3/3! + 223*x^4/4! + 1753*x^5/5! +...
such that, by definition:
A(x) = 1 + d/dx (x+x^2)^2/2! + d^2/dx^2 (x+x^2)^4/4! + d^3/dx^3 (x+x^2)^6/6! + d^4/dx^4 (x+x^2)^8/8! + d^5/dx^5 (x+x^2)^10/10! +...
Compare to the trivial identity:
exp(x) = 1 + d/dx x^2/2! + d^2/dx^2 x^4/4! + d^3/dx^3 x^6/6! + d^4/dx^4 x^8/8! + d^5/dx^5 x^10/10! +...

Prog

(PARI) {Dx(n, F)=local(D=F); for(i=1, n, D=deriv(D)); D}
{a(n)=local(A=x); A=1+sum(m=1, n, Dx(m, (x+x^2+x*O(x^n))^(2*m)/(2*m)!)); n!*polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))

Crossrefs

Cf. A215128.

Sequence in context: A064306 A292427 A333565 * A204706 A197995 A207150

Adjacent sequences: A215122 A215123 A215124 * A215126 A215127 A215128

Keyword

nonn

Author

Paul D. Hanna, Aug 04 2012

Status

approved