A026070 a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, |s(i) - s(i-1)| = 1 for i = 1,2; |s(i) - s(i-1)| <= 1 for i >= 3, s(n) = 3. Also a(n) = T(n,n-3), where T is the array defined in A024996.

1, 2, 8, 24, 76, 232, 707, 2136, 6429, 19282, 57695, 172316, 513955, 1531362, 4559271, 13566288, 40349619, 119972214, 356634978, 1059985776, 3150165270, 9361450868, 27819215185, 82670528056, 245680350995, 730149455646, 2170105711452

Offset

3,2

Links

Table of n, a(n) for n=3..29.

Formula

Conjecture: (n+3)*a(n) +(-5*n-6)*a(n-1) +(3*n-11)*a(n-2) +(11*n-8)*a(n-3) +2*(-2*n+17)*a(n-4) +6*(-n+6)*a(n-5)=0. - R. J. Mathar, Jun 23 2013

Crossrefs

First differences of A025181. Second differences of A014532.

Sequence in context: A231200 A066973 A130495 * A093833 A228404 A006952

Adjacent sequences: A026067 A026068 A026069 * A026071 A026072 A026073

Keyword

nonn

Author

Clark Kimberling

Status

approved