A026086 Number of (s(0), s(1), ..., s(n)) such that s(0) = 0, |s(i) - s(i-1)| = 1 for i = 1,2,3; |s(i) - s(i-1)| <= 1 for i >= 4, s(n) = 3; also a(n) = T(n,n-3), where T is the array defined in A026082.

1, 6, 16, 52, 156, 475, 1429, 4293, 12853, 38413, 114621, 341639, 1017407, 3027909, 9007017, 26783331, 79622595, 236662764, 703350798, 2090179494, 6211285598, 18457764317, 54851312871, 163009822939, 484469104651, 1439956255806

Offset: 4

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

First differences of A026070.

Formula

Conjecture: (n+3)*a(n) +5*(-n-1)*a(n-1) +3*(n-5)*a(n-2) +(11*n-9)*a(n-3) +4*(-n+11)*a(n-4) +6*(-n+7)*a(n-5)=0. - R. J. Mathar, Jun 23 2013