A011878 a(n) = floor( n(n-1)/25 ).

0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 37, 39, 42, 44, 47, 50, 53, 56, 59, 62, 65, 68, 72, 75, 79, 82, 86, 90, 94, 98, 102, 106, 110, 114, 118, 123, 127, 132, 136, 141, 146, 151

Offset

0,9

Links

G. C. Greubel, Table of n, a(n) for n = 0..300

Index entries for linear recurrences with constant coefficients, signature (2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1).

Formula

From R. J. Mathar, Apr 15 2010 (Start)

a(n) = +2*a(n-1) -a(n-2) +a(n-25) -2*a(n-26) +a(n-27).

G.f.: x^6*(x^4-x^3+x^2-x+1)*(x^4+1)*(x^8-x^4+1) / ( (1-x)^3*(1+x^4+x^3+x^2+x)*(1+x^20+x^15+x^10+x^5) ). (End)

Mathematica

Table[Floor[n(n-1)/25], {n, 0, 600}] (* G. C. Greubel, Sep 03 2015 *)
LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 18, 20, 22, 24, 26}, 70] (* Harvey P. Dale, Jul 08 2020 *)

Prog

(PARI) a(n) = n*(n-1)\25; \\ G. C. Greubel, Sep 03 2015

Crossrefs

Sequence in context: A034138 A254667 A011879 * A017896 A118868 A017885

Adjacent sequences: A011875 A011876 A011877 * A011879 A011880 A011881

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved