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A113283
Even bisection of A113281: a(n) = A113281(2*n).
4
1, 3, 11, 51, 255, 1325, 7039, 37951, 206799, 1135969, 6279509, 34889553, 194664283, 1089943229, 6120967411, 34463104999, 194474062663, 1099571123853, 6227893795649, 35329149864161, 200691916063033, 1141489886332555
OFFSET
0,2
FORMULA
G.f.: ( (1+x)/(1-x)/(1-6*x+x^2)*(1-x+(1-6*x+x^2)^(1/2))/2 )^(1/2).
a(n) ~ (1 + sqrt(2))^(2*n + 1/2) / (2*sqrt(Pi*n)). - Vaclav Kotesovec, Oct 18 2020
PROG
(PARI) {a(n)=local(x=X+X*O(X^n)); polcoeff( ((1+x)/(1-x)/(1-6*x+x^2)*(1-x+(1-6*x+x^2)^(1/2))/2)^(1/2), n, X)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 22 2005
STATUS
approved