A026381 T(n,n-2), where T is the array in A026374.

1, 4, 11, 17, 30, 39, 58, 70, 95, 110, 141, 159, 196, 217, 260, 284, 333, 360, 415, 445, 506, 539, 606, 642, 715, 754, 833, 875, 960, 1005, 1096, 1144, 1241, 1292, 1395, 1449, 1558, 1615, 1730, 1790, 1911, 1974, 2101, 2167, 2300

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 2..1000
• Index entries for linear recurrences with constant coefficients, signature (1,2,-2,-1,1).

Programs

Haskell

a026381 = flip a026374 2  -- Reinhard Zumkeller, Feb 22 2014

Mathematica

Drop[CoefficientList[Series[z^2(1+3z+5z^2)/((1-z)^3(1+z)^2),{z,0,50}],z],2] (* or *) LinearRecurrence[{1,2,-2,-1,1},{1,4,11,17,30},50] (* Harvey P. Dale, Dec 31 2021 *)

Formula

G.f.: z^2*(1+3z+5z^2)/[(1-z)^3*(1+z)^2]. - Emeric Deutsch, Jan 25 2004