A008363 a(n) = floor(n/5)*ceiling(n/5).

0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 4, 6, 6, 6, 6, 9, 12, 12, 12, 12, 16, 20, 20, 20, 20, 25, 30, 30, 30, 30, 36, 42, 42, 42, 42, 49, 56, 56, 56, 56, 64, 72, 72, 72, 72, 81, 90, 90, 90, 90, 100, 110, 110, 110, 110, 121, 132, 132

Offset

0,7

Links

Table of n, a(n) for n=0..57.

Formula

From R. J. Mathar, Mar 11 2012: (Start)

a(n) = a(n-1) +2 a(n-5) -2 a(n-6) -a(n-10) +a(n-11).

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

Crossrefs

Sequence in context: A216393 A045812 A064877 * A261611 A097198 A126663

Adjacent sequences: A008360 A008361 A008362 * A008364 A008365 A008366

Keyword

nonn

Author

N. J. A. Sloane

Status

approved