OFFSET
0,1
LINKS
D. Shanks, Generalized Euler and class numbers. Math. Comp. 21 (1967) 689-694.
D. Shanks, Corrigenda to: "Generalized Euler and class numbers", Math. Comp. 22 (1968), 699.
Eric Weisstein's World of Mathematics, Euler Number.
FORMULA
a(n) = (2*n)!*[x^(2*n)](sec(9*x)*2*cos(3*x)^2). - Peter Luschny, Nov 21 2021
MAPLE
egf := sec(9*x)*2*cos(3*x)^2: ser := series(egf, x, 24):
seq((2*n)!*coeff(ser, x, 2*n), n = 0..10); # Peter Luschny, Nov 21 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Aug 31 2001
STATUS
approved