A181343 a(n) = (35*n^4 - 35*n^3 + 55*n^2 - 25*n + 6)/6.

6, 76, 386, 1251, 3126, 6606, 12426, 21461, 34726, 53376, 78706, 112151, 155286, 209826, 277626, 360681, 461126, 581236, 723426, 890251, 1084406, 1308726, 1566186, 1859901, 2193126, 2569256, 2991826, 3464511, 3991126, 4575626

Offset: 1

Author

Klaus Brockhaus, Oct 14 2010

Keywords

• nonn
• easy

Comments

Second bisection of A175898.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).

Crossrefs

Cf. A175898, A181342.

Programs

Magma

[ (35*n^4-35*n^3+55*n^2-25*n+6)/6: n in [1..30] ];

Mathematica

LinearRecurrence[{5,-10,10,-5,1},{6,76,386,1251,3126},30] (* Harvey P. Dale, Dec 06 2016 *)

PARI

a(n)=(35*n^4-35*n^3+55*n^2-25*n+6)/6 \\ Charles R Greathouse IV, Jul 06 2017

Formula

a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) + 140 for n > 4; a(1)=6, a(2)=76, a(3)=386, a(4)=1251.

G.f.: x*(6 + 46*x + 66*x^2 + 21*x^3 + x^4)/(1-x)^5.

a(-n+1) = A181342(n). - Bruno Berselli, Aug 23 2011