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A140505 Second differences of Jacobsthal sequence A001045, pairs with even and odd indices swapped. 2
2, -1, 4, 0, 12, 4, 44, 20, 172, 84, 684, 340, 2732, 1364, 10924, 5460, 43692, 21844, 174764, 87380, 699052, 349524, 2796204, 1398100, 11184812, 5592404, 44739244, 22369620, 178956972, 89478484, 715827884, 357913940, 2863311532, 1431655764, 11453246124 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The second differences are -1, 2, 0, 4, 4, 12, 20, 44, ... (-1)^(n+1)*A084247(n), essentially A097073, which are listed here with -1 <=> 2, 0 <=> 4 etc. swapped in pairs.

LINKS

Table of n, a(n) for n=0..34.

FORMULA

a(n) = 4*A092808(n-2), n>1.

a(n+1) - 2a(n) = (-1)^n*A140504(n).

O.g.f.: (2+x-5x^2)/[(1+x)(1-2x)(1+2x)]. - R. J. Mathar, Jul 08 2008

CROSSREFS

Sequence in context: A077979 A122161 A067164 * A117971 A220420 A190616

Adjacent sequences:  A140502 A140503 A140504 * A140506 A140507 A140508

KEYWORD

sign,less

AUTHOR

Paul Curtz, Jun 30 2008

EXTENSIONS

Edited by R. J. Mathar, Jul 08 2008

STATUS

approved

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Last modified December 8 17:06 EST 2016. Contains 278946 sequences.