A194349 E.g.f.: -log( sqrt(1-x^2) - x ).

1, 2, 5, 24, 129, 960, 7965, 80640, 903105, 11612160, 163451925, 2554675200, 43259364225, 797058662400, 15764670046125, 334764638208000, 7571150452490625, 182111963185152000, 4634731528895593125, 124564582818643968000

Offset

1,2

Comments

Compare e.g.f. to arccosh(x) = log(sqrt(x^2-1) + x).

Links

Table of n, a(n) for n=1..20.

Formula

a(2*n) = 2^n*(2*n-1)! for n>=1.

a(n) = A100097(n+1)*(n-1)!/2^n for n>=1.

a(n) = (n-1)!/2^n * Sum_{k=0..floor((n+1)/2)} C(n+1,k)*A000129(n+1-2*k) for n >= 1. [From a formula of Paul Barry in A100097]

E.g.f.: log( (sqrt(1-x^2) + x)/(1-2*x^2) ).

Example

E.g.f.: A(x) = x + 2*x^2/2! + 5*x^3/3! + 24*x^4/4! + 129*x^5/5! + ...
where
exp(A(x)) = 1 + 2*(x/2) + 6*(x/2)^2 + 16*(x/2)^3 + 46*(x/2)^4 + 128*(x/2)^5 + ... + A098617(n)*(x/2)^n + ...

Mathematica

With[{nn=30}, Rest[CoefficientList[Series[-Log[Sqrt[1-x^2]-x], {x, 0, nn}], x] Range[0, nn]!]] (* Harvey P. Dale, Dec 01 2011 *)

Prog

(PARI) {a(n)=n!*polcoeff(-log(sqrt(1-x^2+x*O(x^n))-x), n)}
(PARI) {A000129(n)=polcoeff(x/(1-2*x-x^2+x*O(x^n)), n)}
{a(n)=if(n<1, 0, sum(k=0, floor((n+1)/2), binomial(n+1, k)*A000129(n+1-2*k))*(n-1)!/2^n)}

Crossrefs

Cf. A098617, A100097.

Sequence in context: A185056 A346204 A330512 * A208969 A020022 A026073

Adjacent sequences: A194346 A194347 A194348 * A194350 A194351 A194352

Keyword

nonn

Author

Paul D. Hanna, Aug 21 2011

Status

approved