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

1,2

Links

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

Formula

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

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 *)

Crossrefs

Cf. A027011.

Sequence in context: A050120 A039010 A127208 * A120365 A166375 A177041

Adjacent sequences: A027019 A027020 A027021 * A027023 A027024 A027025

Keyword

nonn

Author

Clark Kimberling

Status

approved