A215108 a(n) = A215082(2*n)

0, 1, 4, 8, 17, 35, 66, 124, 229, 414, 742, 1318, 2320, 4059, 7062, 12224, 21071, 36185, 61930, 105678, 179847, 305326, 517212, 874380, 1475472, 2485573, 4180648, 7021544, 11777117, 19728911, 33011202

Offset

0,3

Links

Table of n, a(n) for n=0..30.

Formula

a(n) = a(n-1) + 2*a(n-2) + a(n-3) - 2*a(n-4) - 3*a(n-5) -a(n-6), a(0) = 0, a(1) = 1, a(2) = 4, a(3) = 8, a(4) = 17, a(5) = 35 .

G.f.: x*(x+1)*(2x+1)/((x^2+x+1)*(x^2+x-1)^2)

Crossrefs

Cf. A000045, A023607

Sequence in context: A301145 A008372 A005697 * A307545 A115618 A019479

Adjacent sequences: A215105 A215106 A215107 * A215109 A215110 A215111

Keyword

nonn,easy

Author

Philippe Deléham, Aug 03 2012

Status

approved