OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..100
FORMULA
a(n) = (4*n+1)^(n-1) * (4*n)!/(n!*(4!)^n).
E.g.f.: (1/x)*Series_Reversion( x*exp(-x^4/4!) ).
Powers of e.g.f.: define a(n,m) by A(x)^m = Sum_{n>=0} a(n,m)*x^(4*n)/(4*n)!
then a(n,m) = m*(4*n+m)^(n-1) * (4*n)!/(n!*(4!)^n).
EXAMPLE
E.g.f.: A(x) = 1 + x^4/4! + 315*x^8/8! + 975975*x^12/12! + ...
where log(A(x)) = x^4*A(x)^4/4! and
A(x)^4 = 1 + 4*x^4/4! + 1680*x^8/8! + 5913600*x^12/12! + 84084000000*x^16/16! + ...
MATHEMATICA
Table[(4*n + 1)^(n - 1)*(4*n)!/(n!*(4!)^n), {n, 0, 30}] (* G. C. Greubel, Jul 27 2018 *)
PROG
(PARI) {a(n)=(4*n)!*polcoeff(1/x*serreverse(x*(exp(-x^4/4!+x*O(x^(4*n))))), 4*n)}
(PARI) {a(n)=(4*n+1)^(n-1)*(4*n)!/(n!*(4!)^n)};
(Magma) [(4*n+1)^(n-1)*Factorial(4*n)/(24^n*Factorial(n)): n in [0..30]]; // G. C. Greubel, Jul 27 2018
(GAP) List([0..10], n->(4*n+1)^(n-1)*Factorial(4*n)/(Factorial(n)*Factorial(4)^n)); # Muniru A Asiru, Jul 28 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 15 2011
STATUS
approved