A181079 a(n) = Sum_{k=0..n-1} binomial(n-1,k)^(n-1) * n/(n-k).

1, 3, 10, 95, 3126, 363132, 154742736, 238830058287, 1401973344195850, 30168336369959767298, 2525043541826640689536056, 779938173975597096091742711900, 951131113887078985926203597341181404

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..60

Formula

L.g.f.: L(x) = Sum_{n>=1} [ Sum_{k>=0} C(n+k-1,k)^(n+k-1)*x^k ] *x^n/n.

Logarithmic derivative of A181076.

Example

L.g.f.: L(x) = x + 3*x^2/2 + 10*x^3/3 + 95*x^4/4 + 3126*x^5/5 + ...
which equals the series:
L(x) = (1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + ...)*x
+ (1 + 2^2*x + 3^3*x^2 + 4^4*x^3 + 5^5*x^4 + 6^6*x^5 + ...)*x^2/2
+ (1 + 3^3*x + 6^4*x^2 + 10^5*x^3 + 15^6*x^4 + 21^7*x^5 + ...)*x^3/3
+ (1 + 4^4*x + 10^5*x^2 + 20^6*x^3 + 35^7*x^4 + 56^8*x^5 + ...)*x^4/4
+ (1 + 5^5*x + 15^6*x^2 + 35^7*x^3 + 70^8*x^4 + 126^9*x^5 + ...)*x^5/5
+ (1 + 6^6*x + 21^7*x^2 + 56^8*x^3 + 126^9*x^4 + 252^10*x^5 + ...)*x^6/6
+ (1 + 7^7*x + 28^8*x^2 + 84^9*x^3 + 210^10*x^4 + 462^11*x^5 + ...)*x^7/7 + ...
Exponentiation yields the g.f. of A181078:
exp(L(x)) = 1 + x + 2*x^2 + 5*x^3 + 29*x^4 + 657*x^5 + 61207*x^6 + … + A181078(n)*x^n + ...

Mathematica

Table[Sum[Binomial[n-1, k]^(n-1) n/(n-k), {k, 0, n-1}], {n, 20}] (* Harvey P. Dale, Jun 13 2013 *)

Prog

(PARI) {a(n)=sum(k=0, n-1, binomial(n-1, k)^(n-1)*n/(n-k))}
(PARI) {a(n)=n*polcoeff(sum(m=1, n, sum(k=0, n, binomial(m+k-1, k)^(m+k-1)*x^k)*x^m/m)+x*O(x^n), n)}
(Magma) [(&+[Binomial(n-1, j)^(n-1)*(n/(n-j)): j in [0..n-1]]): n in [1..20]]; // G. C. Greubel, Apr 04 2021
(Sage) [sum( binomial(n-1, k)^(n-1)*(n/(n-k)) for k in (0..n-1)) for n in (1..20)] # G. C. Greubel, Apr 04 2021

Crossrefs

Cf. A181078 (exp), variants: A181071, A181075, A181077.

Sequence in context: A073733 A005205 A216450 * A240512 A065924 A013233

Adjacent sequences: A181076 A181077 A181078 * A181080 A181081 A181082

Keyword

nonn

Author

Paul D. Hanna, Oct 03 2010

Status

approved