A248155 Expansion of (1 + x - x^2)/((1 + x)*(1 + 2*x)).

1, -2, 3, -5, 9, -17, 33, -65, 129, -257, 513, -1025, 2049, -4097, 8193, -16385, 32769, -65537, 131073, -262145, 524289, -1048577, 2097153, -4194305, 8388609, -16777217, 33554433, -67108865, 134217729, -268435457, 536870913

Offset

0,2

Comments

Alternating row sums of A105810. Riordan triangle ((1 + x - x^2)/(1 + x)^2, x/(1 + x)).

Links

Table of n, a(n) for n=0..30.

Index entries for linear recurrences with constant coefficients, signature (-3,-2).

Formula

O.g.f.: (1+x-x^2)/((1+x)*(1+2*x)).

a(n) = (3/2)*b(n) + (5/2)*b(n-1), n>=1, a(0) = 1, with b(n) = A225883(n+1).

a(n) = (-1)^n*(1 + 2^(n-1)), n>=1, a(0) = 1.

Prog

(PARI) Vec((1 + x - x^2)/((1 + x)*(1 + 2*x)) + O (x^40)) \\ Michel Marcus, Oct 11 2014

Crossrefs

Cf. A105810, A094373.

Sequence in context: A005257 A091697 A109740 * A000051 A094373 A213705

Adjacent sequences: A248152 A248153 A248154 * A248156 A248157 A248158

Keyword

sign,easy

Author

Wolfdieter Lang, Oct 04 2014

Status

approved