A011907 [ n(n-1)(n-2)/25 ].

0, 0, 0, 0, 0, 2, 4, 8, 13, 20, 28, 39, 52, 68, 87, 109, 134, 163, 195, 232, 273, 319, 369, 425, 485, 552, 624, 702, 786, 876, 974, 1078, 1190, 1309, 1436, 1570, 1713, 1864, 2024, 2193, 2371, 2558, 2755, 2961

Offset

0,6

Links

Table of n, a(n) for n=0..43.

Index entries for linear recurrences with constant coefficients, signature (3, -3, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -3, 3, -1).

Formula

a(n) = +3*a(n-1) -3*a(n-2) +a(n-3) +a(n-25) -3*a(n-26) +3*a(n-27) -a(n-28). G.f.: x^5*(2-2*x+2*x^2-x^3+x^4-x^5+2*x^6-x^7+x^8+x^12-x^13+2*x^14-x^15+x^16-x^17+2*x^18-2*x^19+3*x^20-2*x^21+x^22) / ( (-1+x)^4*(1+x^4+x^3+x^2+x)*(x^20+x^15+x^10+x^5+1) ). - R. J. Mathar, Apr 15 2010

Mathematica

Table[Floor[(n(n-1)(n-2))/25], {n, 0, 60}] (* or *) LinearRecurrence[{3, -3, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -3, 3, -1}, {0, 0, 0, 0, 0, 2, 4, 8, 13, 20, 28, 39, 52, 68, 87, 109, 134, 163, 195, 232, 273, 319, 369, 425, 485, 552, 624, 702}, 60] (* Harvey P. Dale, Aug 25 2021 *)

Prog

(PARI) a(n)=n*(n-1)*(n-2)\25 \\ Charles R Greathouse IV, Oct 21 2022

Crossrefs

Sequence in context: A245094 A164486 A084684 * A056133 A172131 A173721

Adjacent sequences: A011904 A011905 A011906 * A011908 A011909 A011910

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved