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A121588 G.f.: A(x) = 1+x*(1+x*(1+x*(...(1+x*(...)^(-2^n) )...)^-4)^-2)^-1. 0
1, 1, -1, 3, -16, 145, -2347, 72498, -4459887, 554300965, -139235329270, 70475747813447, -71685052573258824, 146249172542467865074, -597744865134782025119044, 4890851047359454263328433041, -80078758027845307168595201926254 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Limit |a(n)|/2^[(n-1)*(n-2)/2] = 1.97254925752982255...

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

G.f.: A(x) = 1 + x/B(x); B(x) = 1 + x/C(x)^2; C(x) = 1 + x/D(x)^4;

D(x) = 1 + x/E(x)^8; E(x) = 1 + x/F(x)^16; ...

where the respective sequences begin:

B=[1,1,-2,11,-112,2025,-67324,4305909,-545113744,...];

C=[1,1,-4,42,-836,30259,-2041616,265712044,-68214603840,...];

D=[1,1,-8,164,-6456,467850,-63614840,16702037652,...];

E=[1,1,-16,648,-50736,7358500,-2008876560,1059405119352,...];

F=[1,1,-32,2576,-402272,116732040,-63860549280,...].

PROG

(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(j=0, n, A=1+x/A^(2^(n-j))); polcoeff(A, n)}

CROSSREFS

Cf. A120959 (variant).

Sequence in context: A109398 A294003 A006058 * A331538 A306397 A264660

Adjacent sequences: A121585 A121586 A121587 * A121589 A121590 A121591

KEYWORD

sign

AUTHOR

Paul D. Hanna, Aug 09 2006

STATUS

approved

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Last modified January 27 10:15 EST 2023. Contains 359838 sequences. (Running on oeis4.)