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A064070
Generalized Euler number c(9,n).
5
2, 126, 49410, 48649086, 89434106370, 264235243691646, 1145011717430672130, 6841110155700330881406, 53899295662946509072626690, 541439307193573593050370186366, 6754273504043546592593642328610050, 102439130403410639137159601119206854526
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
MATHEMATICA
Range[0, 22, 2]! CoefficientList[Series[2 Sec[9 x] Cos[3 x]^2, {x, 0, 22}], x^2] (* Matthew House, Oct 27 2024 *)
CROSSREFS
Row 9 of A235605.
Sequence in context: A237994 A348159 A157070 * A266993 A364654 A139904
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Aug 31 2001
STATUS
approved