A187012 Antidiagonal sums of A103516.

1, 2, 5, 4, 8, 6, 11, 8, 14, 10, 17, 12, 20, 14, 23, 16, 26, 18, 29, 20, 32, 22, 35, 24, 38, 26, 41, 28, 44, 30, 47, 32, 50, 34, 53, 36, 56, 38, 59, 40, 62, 42, 65, 44, 68, 46, 71, 48, 74, 50, 77, 52, 80, 54, 83, 56, 86, 58, 89, 60, 92, 62, 95, 64

Offset: 2

Author

Michel Marcus, Aug 30 2013

Keywords

• nonn
• easy

Comments

This sequence differs from A081556 at least for n=24 (see comment about n=24 in A081556).

Links

• Vincenzo Librandi, Table of n, a(n) for n = 2..1000

Programs

Mathematica

CoefficientList[Series[(1 + 2 x + 3 x^2 - x^4)/((1 - x)^2 (1 + x)^2), {x, 0, 40}], x] (* Vincenzo Librandi, Jun 24 2014 *)

PARI

a(n) = sum(k=0, n\2, 0^(k*(n-2*k))*(n-k+1)); \\ Michel Marcus, Aug 30 2013

Formula

a(n) = sum{k=0..floor(n/2), 0^(k(n-2k))*(n-k+1)}. - Paul Barry, Aug 30 2013

G.f. : x^2*(1+2*x+3*x^2-x^4)/((1-x)^2*(1+x)^2).

a(n) = A080512(n) - 1 for n>2.