A362156 Expansion of -1/(1 - x * sqrt(1-4*x)).

-1, -1, 1, 5, 9, 11, 17, 59, 237, 849, 2861, 9625, 33057, 115753, 410581, 1469325, 5296449, 19216691, 70134489, 257320475, 948545125, 3511308899, 13047504065, 48649662439, 181967395749, 682578873479, 2567177040641, 9678602093387, 36571567691029

Offset: 0

Author

Seiichi Manyama, Apr 09 2023

Keywords

• sign
• easy

Crossrefs

Cf. A000984, A362157.

Programs

PARI

my(N=30, x='x+O('x^N)); Vec(-1/(1-x*sqrt(1-4*x)))

Formula

a(n) = -Sum_{k=0..n} (-4)^k * binomial((n-k)/2,k).