OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..182
FORMULA
a(n) = (-1)^n*(2+4*n)!/(2*(1+2*n)!) = (-1)^n*A001813(2*n+1)/2. - Robert Israel, Dec 21 2015
MAPLE
seq(i!*coeff(series(sin(x^2)/2, x, 4*i+4), x, i), i=2..54, 4); # Peter Luschny, Dec 14 2012
MATHEMATICA
nmax = 12; coes = CoefficientList[ Series[ Sin[x^2]/2, {x, 0, 4*nmax + 2}], x]; a[n_] := coes[[4*n + 3]]*(4*n + 2)!; Table[a[n], {n, 0, nmax}] (* Jean-François Alcover, Dec 14 2012 *)
Table[(-1)^n (2 + 4 n)!/(2 (1 + 2 n)!), {n, 0, 25}] (* Vincenzo Librandi, Dec 22 2015 *)
PROG
(Sage)
def A009564(n):
return falling_factorial(4*n+2, 2*n+1)/(2*(-1)^n)
[A009564(n) for n in (0..12)] # Peter Luschny, Dec 14 2012
(Magma) [(-1)^n*Factorial(2+4*n)/(2*Factorial(1+2*n)): n in [0..20]]; // Vincenzo Librandi, Dec 22 2015
(PARI) a(n) = (-1)^n*(2+4*n)!/(2*(1+2*n)!); \\ Altug Alkan, Dec 22 2015
CROSSREFS
KEYWORD
sign
AUTHOR
EXTENSIONS
Extended with signs Mar 1997
Definition corrected and terms a(10)-a(12) from Peter Luschny, Dec 14 2012
STATUS
approved