A256960 a(0)=1, a(1)=4; thereafter a(n) = a(n-2)+2*A055099(n-1)+2^(n-1).

1, 4, 11, 36, 119, 408, 1419, 4988, 17631, 62528, 222163, 790180, 2812135, 10011304, 35647259, 126942540, 452078447, 1610033040, 5734081251, 20421960308, 72733344375, 259042555640, 922591559467, 3285854197276, 11702734525951, 41679889602784, 148445093121011, 528694969090116

Offset: 0

Author

N. J. A. Sloane, Apr 14 2015

Keywords

• nonn
• easy

Links

• Colin Barker, Table of n, a(n) for n = 0..1000
• J. Goldwasser et al., The density of ones in Pascal's rhombus, Discrete Math., 204 (1999), 231-236.
• Paul K. Stockmeyer, The Pascal Rhombus and the Stealth Configuration, arXiv:1504.04404 [math.CO], 2015.
• Index entries for linear recurrences with constant coefficients, signature (4,1,-8,-4).

Crossrefs

Cf. A055099.

Programs

PARI

Vec(-(2*x+1)*(2*x^2+2*x-1)/((x+1)*(2*x-1)*(2*x^2+3*x-1)) + O(x^100)) \\ Colin Barker, Jun 06 2015

Formula

G.f.: -(2*x+1)*(2*x^2+2*x-1) / ((x+1)*(2*x-1)*(2*x^2+3*x-1)). - Colin Barker, Jun 05 2015