A025182 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) = 4. Also a(n) = T(n,n-4), where T is the array defined in A025177.

1, 4, 16, 56, 189, 616, 1968, 6192, 19272, 59488, 182468, 556920, 1693146, 5131296, 15511344, 46791072, 140905197, 423709956, 1272596136, 3818355464, 11447074309, 34292702840, 102670377120, 307230479920, 918951019155, 2747624937876

Offset: 4

Author

Clark Kimberling

Keywords

• nonn

Comments

Apparently first differences of A014533.

Crossrefs

Cf. A014533, A025177.

Formula

Conjecture: -(n-4)*(n+4)*a(n) +(4*n^2-7*n-29)*a(n-1) +(-2*n^2+17*n-2)*a(n-2) -(4*n+1)*(n-3)*a(n-3) +3*(n-3)*(n-4)*a(n-4)=0. - R. J. Mathar, Feb 25 2015

Conjecture: -(n-4)*(n+4)*(n^2-3*n+6)*a(n) +(n-1)*(2*n^3-5*n^2+11*n-36)*a(n-1) +3*(n-1)*(n-2)*(n^2-n+4)*a(n-2)=0. - R. J. Mathar, Feb 25 2015