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A011867
a(n) = floor(n*(n-1)/14).
3
0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 9, 11, 13, 15, 17, 19, 21, 24, 27, 30, 33, 36, 39, 42, 46, 50, 54, 58, 62, 66, 70, 75, 80, 85, 90, 95, 100, 105, 111, 117, 123, 129, 135, 141, 147, 154, 161, 168, 175, 182, 189, 196, 204, 212, 220, 228, 236, 244, 252, 261, 270, 279, 288, 297
OFFSET
0,7
FORMULA
From R. J. Mathar, Apr 15 2010: (Start)
a(n) = 2*a(n-1) - a(n-2) + a(n-7) - 2*a(n-8) + a(n-9).
G.f.: x^5 / ((1-x)^3*(x^6+x^5+x^4+x^3+x^2+x+1) ). (End)
MATHEMATICA
Table[Floor[n(n - 1)/14], {n, 0, 59}] (* Alonso del Arte, Aug 26 2011 *)
LinearRecurrence[{2, -1, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 1, 2, 3, 4}, 70] (* Harvey P. Dale, Oct 22 2016 *)
PROG
(Magma) [Floor(n*(n-1)/14): n in [0..70]]; // Vincenzo Librandi, Aug 29 2011
CROSSREFS
Sequence in context: A280693 A281613 A174738 * A008725 A275673 A347327
KEYWORD
nonn,easy
STATUS
approved