A124495 G.f.: A(x) = 1/[1-x - Sum_{n>=1} A001147(n)*x^(2n) ] where A001147(n) = (2n)!/(n!*2^n) is the double factorials.

1, 1, 2, 3, 8, 14, 43, 81, 283, 556, 2243, 4512, 21374, 43469, 243817, 497217, 3289606, 6697795, 51583952, 104698998, 922789643, 1867079621, 18522929815, 37380015420, 411572179999, 828925168492, 10014624164666, 20140445929353

Offset

0,3

Comments

Is this sequence equal to A076876 (meandric numbers for a river crossing two parallel roads at n points)?

Links

Table of n, a(n) for n=0..27.

Example

G.f.: A(x) = 1/(1-x - x^2 - 3*x^4 - 15*x^6 - 105*x^8 - 945*x^10 -...).

Prog

(PARI) a(n)=polcoeff(1/(1-x-sum(k=1, n\2, (2*k)!/k!/2^k*x^(2*k))+x*O(x^n)), n)

Crossrefs

Cf. A001147.

Sequence in context: A107321 A005316 A076876 * A007919 A249167 A205101

Adjacent sequences: A124492 A124493 A124494 * A124496 A124497 A124498

Keyword

nonn

Author

Paul D. Hanna, Nov 04 2006

Status

approved