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A126151 E.g.f.: ( (1 + cos(sqrt(6)*x))/2 )^(-1/3), showing coefficients of only the even powers of x. 5
1, 1, 6, 96, 2976, 151416, 11449296, 1204566336, 168233625216, 30110372009856, 6719377991060736, 1829013279998846976, 596449130341224185856, 229556544889929225117696, 102956750031135241952280576 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Previous name was: Column 0 and row sums of symmetric triangle A126150.

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..232

E. Norton, Symplectic Reflection Algebras in Positive Characteristic as Ore Extensions, arXiv preprint arXiv:1302.5411 [math.RA], 2013.

FORMULA

a(n)=Sum_{k, 0<=k<=n}A087736(n,k)*2^(n-k). - Philippe Deléham, Jul 17 2007

G.f.: 1/(1-x/(1-5*x/(1-12*x/(1-22*x/(1-35*x/(1-51*x/(1-70*x/(1-...- (n*(3*n-1)/2)*x/(1-...))))))))), a continued fraction involving pentagonal numbers A000326. - Paul D. Hanna, Feb 15 2012

E.g.f. satisfies: A(x) = exp( Integral Integral A(x)^3 dx dx ), where A(x) = Sum_{n>=0} a(n)*x^(2*n)/(2*n)! and the constant of integration is zero. - Paul D. Hanna, May 29 2015

E.g.f. satisfies: A(x) = exp( Integral A(x)^(3/2) * Integral 1/A(x)^(3/2) dx dx ),  where A(x) = Sum_{n>=0} a(n)*x^(2*n)/(2*n)! and the constant of integration is zero. - Paul D. Hanna, Jun 02 2015

a(n) ~ Gamma(1/3) * 2^(3*n+4/3) * 3^(n+1/2) * n^(2*n+1/6) / (exp(2*n) * Pi^(2*n+7/6)). - Vaclav Kotesovec, May 30 2015

EXAMPLE

E.g.f.: A(x) = 1 + x^2/2! + 6*x^4/4! + 96*x^6/6! + 2976*x^8/8! + 151416*x^10/10! +...

where the logarithm begins:

log(A(x)) = x^2/2! + 3*x^4/4! + 36*x^6/6! + 918*x^8/8! + 40176*x^10/10! + 2686608*x^12/12! +...

compare the logarithm to

A(x)^3 = 1 + 3*x^2/! + 36*x^4/4! + 918*x^6/6! + 40176*x^8/8! + 2686608*x^10/10! +...

where A(x)^3 = 2/(1 + cos(sqrt(6)*x)).

MATHEMATICA

terms = 18;

CoefficientList[((1 + Cos[Sqrt[6] x])/2)^(-3^(-1)) + O[x]^(2 terms), x] Range[0, 2 terms - 2]! // DeleteCases[#, 0]& (* Jean-François Alcover, Jul 26 2018 *)

PROG

(PARI) /* Continued Fraction involving pentagonal numbers A000326: */

{a(n)=local(CF=1+x*O(x), m, P); for(k=1, n, m=n-k+1; P=m*(3*m-1)/2; CF=1/(1-P*x*CF)); polcoeff(CF, n, x)}

for(n=0, 20, print1(a(n), ", "))

(PARI) /* E.g.f. A(x) = exp( Integral^2 A(x)^3 dx^2 ): */

{a(n)=local(A=1+x*O(x)); for(i=1, n, A=exp(intformal(intformal(A^3 + x*O(x^(2*n))))) ); (2*n)!*polcoeff(A, 2*n, x)}

for(n=0, 20, print1(a(n), ", "))

(PARI) /* E.g.f. A(x) = exp( Integral A(x)^(3/2) * Integral 1/A(x)^(3/2) dx dx ) */

{a(n) = local(A=1+x); for(i=1, n, A = exp( intformal( A^(3/2) * intformal( 1/A^(3/2) + x*O(x^n)) ) ) ); n!*polcoeff(A, n)}

for(n=0, 20, print1(a(2*n), ", "))

CROSSREFS

Cf. A126150; diagonals: A126152, A126153.

Sequence in context: A038094 A304646 A251576 * A066319 A186269 A111826

Adjacent sequences:  A126148 A126149 A126150 * A126152 A126153 A126154

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Dec 19 2006

EXTENSIONS

New name from Paul D. Hanna, May 30 2015

STATUS

approved

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Last modified April 18 10:21 EDT 2021. Contains 343087 sequences. (Running on oeis4.)