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A086456 Expansion of (1+x+sqrt(1-6x+x^2))/2 in powers of x. 4
1, -1, -2, -6, -22, -90, -394, -1806, -8558, -41586, -206098, -1037718, -5293446, -27297738, -142078746, -745387038, -3937603038, -20927156706, -111818026018, -600318853926, -3236724317174, -17518619320890, -95149655201962 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Series reversion of x(Sum_{k>=0} a(k)x^k) is x(Sum_{k>=0} A003168(k)x^k).

G.f. A(x)=Sum_{k>=0} a(k)x^k satisfies 0=2x-(x+1)*A(x)+A(x)^2.

LINKS

Table of n, a(n) for n=0..22.

FORMULA

G.f.: (1+x+sqrt(1-6x+x^2))/2. (=1/g.f. A001003)

PROG

(PARI) a(n)=polcoeff((1+x+sqrt(1-6*x+x^2+x*O(x^n)))/2, n)

CROSSREFS

A minor variation of A006318. a(n)=-A006318(n-1), n>0. a(n)=A085403(n), n>1.

Sequence in context: A165523 A049126 A049134 * A006318 A155069 A103137

Adjacent sequences:  A086453 A086454 A086455 * A086457 A086458 A086459

KEYWORD

sign

AUTHOR

Michael Somos, Jul 20 2003

STATUS

approved

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Last modified December 21 13:45 EST 2014. Contains 252321 sequences.