A025181 a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is an integer, s(0) = 0, |s(1)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2, s(n) = 3. Also a(n) = T(n,n-3), where T is the array defined in A025177.

1, 3, 11, 35, 111, 343, 1050, 3186, 9615, 28897, 86592, 258908, 772863, 2304225, 6863496, 20429784, 60779403, 180751617, 537386595, 1597372371, 4747537641, 14108988509, 41928203694, 124598731750, 370279082745, 1100428538391, 3270534249843

Offset

3,2

Links

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

Formula

Conjecture: +(n+3)*a(n) +(-5*n-7)*a(n-1) +(3*n-7)*a(n-2) +(11*n-7)*a(n-3) +4*(-n+6)*a(n-4) +6*(-n+5)*a(n-5)=0. - R. J. Mathar, Feb 25 2015

Conjecture: -(n+3)*(n-3)*(4*n^2-12*n+17)*a(n) +(n-1)*(8*n^3-20*n^2+30*n-81)*a(n-1) +3*(n-1)*(n-2)*(4*n^2-4*n+9)*a(n-2)=0. - R. J. Mathar, Feb 25 2015

Crossrefs

Cf. A025568.

First differences of A014532. First differences are in A026070.

Sequence in context: A126940 A026125 A026154 * A004054 A068995 A109196

Adjacent sequences: A025178 A025179 A025180 * A025182 A025183 A025184

Keyword

nonn

Author

Clark Kimberling

Status

approved