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

Author

Paul D. Hanna, Nov 04 2006

Keywords

• nonn

Comments

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

Examples

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

Crossrefs

Cf. A001147.

Programs

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)