A328994 a(n) = n^2*(1+n)*(1+n^2)/4.

1, 15, 90, 340, 975, 2331, 4900, 9360, 16605, 27775, 44286, 67860, 100555, 144795, 203400, 279616, 377145, 500175, 653410, 842100, 1072071, 1349755, 1682220, 2077200, 2543125, 3089151, 3725190, 4461940, 5310915, 6284475, 7395856, 8659200, 10089585

Offset: 1

Author

N. J. A. Sloane, Nov 12 2019

Keywords

• nonn
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).

Crossrefs

Cf. A329126, A329000.

Programs

Magma

[(n^2+n^3+n^4+n^5)/4: n in [1..40]] // Vincenzo Librandi, Nov 13 2019

Mathematica

CoefficientList[Series[(1+9x+15x^2+5x^3)/(1-x)^6,{x,0,33}],x] (* Vincenzo Librandi, Nov 13 2019 *)

Formula

From Vincenzo Librandi, Nov 13 2019: (Start)

a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6).

G.f.: x*(1+9*x+15*x^2+5*x^3)/(1-x)^6. (End)