A171129 a(n)=(n^4-n^3-n^2-n)/2.

0, -1, 1, 21, 86, 235, 519, 1001, 1756, 2871, 4445, 6589, 9426, 13091, 17731, 23505, 30584, 39151, 49401, 61541, 75790, 92379, 111551, 133561, 158676, 187175, 219349, 255501, 295946, 341011, 391035, 446369, 507376, 574431, 647921, 728245, 815814

Offset

0,4

Comments

From Chai Wah Wu, Mar 16 2017: (Start)

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n > 4.

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

Links

Table of n, a(n) for n=0..36.

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

Example

(2^4 - 2^3 - 2^2 - 2)/2 = 1, (3^4 - 3^3 - 3^2 - 3)/2 = 21,..

Mathematica

f[n_]:=(n^4-n^3-n^2-n)/2; Table[f[n], {n, 0, 5!}]

Crossrefs

Cf. A152016

Sequence in context: A063651 A220613 A045016 * A301540 A240518 A219850

Adjacent sequences: A171126 A171127 A171128 * A171130 A171131 A171132

Keyword

sign

Author

Vladimir Joseph Stephan Orlovsky, Dec 04 2009

Extensions

Offset corrected by Chai Wah Wu, Mar 16 2017

Status

approved