A074334 a(n) = Sum_{r=1..n} r^4*binomial(n,r)^2.

0, 1, 20, 234, 2144, 16750, 117432, 761460, 4654848, 27173718, 152867000, 834212236, 4438175040, 23108423884, 118111709744, 594059985000, 2946077521920, 14429322555750, 69892354873080, 335194270938780, 1593211647720000, 7511501237722020, 35153884344493200

Offset

0,3

References

H. W. Gould, Combinatorial Identities, 1972. (See formulas 3.77, 3.78, and 3.79 on page 31.)

Links

Andrew Howroyd, Table of n, a(n) for n = 0..200

Nikita Gogin and Mika Hirvensalo, On the Moments of Squared Binomial Coefficients, (2020).

Formula

For n>1 a(n) = n^2*(n^3+n^2-3*n-1)*C(n-2). Here C(n-2) = binomial(2*n-4, n-2)/(n-1) is a Catalan number.

From G. C. Greubel, Jun 23 2022: (Start)

a(n) = (n^2*(n^3 + n^2 - 3*n -1)/(2*(2*n-3)))*binomial(2*n-2, n-1).

G.f.: x*(1 + 2*x + 32*x^3 - 128*x^4 + 144*x^5)/(1-4*x)^(9/2).

E.g.f.: x*exp(2*x)*( (1+2*x)*(1 +6*x +4*x^2)*BesselI(0, 2*x) + 2*x*(2 + 7*x + 4*x^2)*BesselI(1, 2*x) ). (End)

Mathematica

Total/@Table[r^4 Binomial[n, r]^2, {n, 0, 20}, {r, n}] (* Harvey P. Dale, Dec 04 2017 *)
Table[n^2*(n^3+n^2-3*n-1)*CatalanNumber[n-2] -Boole[n==1], {n, 0, 30}] (* G. C. Greubel, Jun 23 2022 *)

Prog

(PARI) vector(30, n, n--; sum(k=1, n, k^4*binomial(n, k)^2)) \\ Michel Marcus, Aug 19 2015
(Magma) [n le 1 select n else n^2*(n^3+n^2-3*n-1)*Catalan(n-2): n in [0..30]]; // G. C. Greubel, Jun 23 2022
(SageMath) [n^2*(n^3+n^2-3*n-1)*catalan_number(n-2) for n in (0..30)] # G. C. Greubel, Jun 23 2022

Crossrefs

Cf. A000108 (Catalan numbers).

Cf. A000984, A002457, A037966, A037972, A329444, A329913.

Sequence in context: A022648 A004315 A253010 * A163004 A278320 A061139

Adjacent sequences: A074331 A074332 A074333 * A074335 A074336 A074337

Keyword

easy,nonn

Author

Paul Boddington, Mar 05 2003

Extensions

Terms a(18) and beyond from Andrew Howroyd, Jan 16 2020

Status

approved