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A349018
G.f. satisfies: A(x) = 1/(1 - x/(1 - x*A(x)))^4.
2
1, 4, 14, 60, 297, 1584, 8868, 51412, 305964, 1858308, 11472152, 71774548, 454080514, 2899959640, 18670920458, 121056521536, 789733186076, 5180002637472, 34141018474400, 225995779077324, 1501809350268648, 10015202238242356, 67003372168525774
OFFSET
0,2
LINKS
FORMULA
If g.f. satisfies: A(x) = 1/(1 - x/(1 - x*A(x))^s)^t, then a(n) = Sum_{k=0..n} binomial(t*n-(t-1)*(k-1),k) * binomial(n+(s-1)*k-1,n-k)/(n-k+1).
a(n) ~ sqrt((1 - r*s)*(1 - r - r*s) / (2 - r*(2*s - 3))) / (sqrt(2*Pi) * n^(3/2) * r^(n+1)), where r = 0.13968480593491705709394976139265608086009606657813769... and s = 3.10146641162846907900664383717504887133026560522911567... are real roots of the system of equations (-1 + r*s)^4/(-1 + r + r*s)^4 = s, (4*r^2*(-1 + r*s)^3)/(-1 + r + r*s)^5 = 1. - Vaclav Kotesovec, Nov 15 2021
PROG
(PARI) a(n, s=1, t=4) = sum(k=0, n, binomial(t*n-(t-1)*(k-1), k)*binomial(n+(s-1)*k-1, n-k)/(n-k+1));
CROSSREFS
Sequence in context: A299926 A307399 A307411 * A259104 A082033 A009339
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 06 2021
STATUS
approved