A088941 a(n)=12*sum(1<=i<=j<=k<=n,i*j/k).

0, 12, 54, 154, 349, 685, 1217, 2009, 3134, 4674, 6720, 9372, 12739, 16939, 22099, 28355, 35852, 44744, 55194, 67374, 81465, 97657, 116149, 137149, 160874, 187550, 217412, 250704, 287679, 328599, 373735, 423367, 477784, 537284, 602174, 672770

Offset: 0

Author

Benoit Cloitre, Oct 25 2003

Keywords

• nonn
• easy

Comments

Always an integer.

Links

• Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).

Crossrefs

Cf. A088942, A088943.

A051798(n) - 1.

Programs

Mathematica

LinearRecurrence[{5,-10,10,-5,1},{0,12,54,154,349},40] (* Harvey P. Dale, May 01 2014 *)

PARI

a(n)=if(n<0,0,a(n)=n/24*(9*n^3 + 58*n^2 + 123*n + 98))

Formula

a(n)=(n/24)*(9*n^3 + 58*n^2 + 123*n + 98).

G.f.: x*(x^3-4*x^2+6*x-12) / (x-1)^5. - Colin Barker, Jun 15 2013