OFFSET
1,2
FORMULA
Logarithmic derivative of A166896.
a(n) ~ sqrt(15) * phi^(3*n + 2) / (6*Pi*n), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Nov 27 2017
EXAMPLE
L.g.f.: L(x) = x + 3*x^2/2 + 13*x^3/3 + 39*x^4/4 + 126*x^5/5 + 477*x^6/6 +...
exp(L(x)) = 1 + x + 2*x^2 + 6*x^3 + 16*x^4 + 45*x^5 + 142*x^6 + 459*x^7 +...+ A166896(n)*x^n/n +...
MATHEMATICA
Table[Sum[Binomial[n-k, k]^3 n/(n-k), {k, 0, Floor[n/2]}], {n, 30}] (* Harvey P. Dale, Mar 05 2013 *)
PROG
(PARI) a(n)=sum(k=0, n\2, binomial(n-k, k)^3*n/(n-k))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 23 2009
STATUS
approved