A011860 a(n) = floor(n*(n-1)/7).

0, 0, 0, 0, 1, 2, 4, 6, 8, 10, 12, 15, 18, 22, 26, 30, 34, 38, 43, 48, 54, 60, 66, 72, 78, 85, 92, 100, 108, 116, 124, 132, 141, 150, 160, 170, 180, 190, 200, 211, 222, 234, 246, 258, 270, 282, 295, 308, 322, 336, 350, 364, 378, 393, 408, 424, 440, 456, 472, 488, 505

Offset

0,6

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

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

Formula

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

a(n) = +2*a(n-1) -a(n-2) +a(n-7) -2*a(n-8) +a(n-9).

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

Mathematica

A011860[n_] := Quotient[n*(n-1), 7]; Array[A011860, 100, 0] (* Paolo Xausa, Jun 05 2026 *)

Crossrefs

Sequence in context: A347009 A130261 A186384 * A259278 A049445 A356448

Adjacent sequences: A011857 A011858 A011859 * A011861 A011862 A011863

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved