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
KEYWORD
nonn,easy
AUTHOR
STATUS
approved