A027022 a(n) = Sum_{k=floor((n+1)/2)..n} T(k,n-k); i.e., a(n) is n-th diagonal sum of left-justified array T given by A027011.

1, 3, 4, 7, 11, 15, 26, 34, 57, 79, 123, 181, 269, 406, 597, 900, 1332, 1991, 2968, 4414, 6596, 9805, 14639, 21792, 32488, 48418, 72130, 107532, 160191, 238776, 355785, 530211, 790156, 1177431, 1754739, 2614807, 3896754, 5806922, 8653577, 12895791

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A027011.

Programs

Mathematica

CoefficientList[Series[(-x^4 - 3 x^3 + x^2 + 3 x + 1) / ((1 - x^2) (1 - 2 x^2 - x^3 + x^4)), {x, 0, 60}], x] (* Vincenzo Librandi, Aug 03 2017 *)

Formula

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