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A084611 a(n) = sum of absolute values of coefficients of (1+x-x^2)^n. 6
1, 3, 7, 13, 35, 83, 165, 367, 899, 1957, 3839, 9771, 22709, 43213, 102963, 255061, 525601, 1098339, 2798273, 6202969, 11746259, 29976073, 70898649, 140495779, 314391789, 787757461, 1688887719, 3337986541, 8583687613, 19647782463 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Limit a(n+1)/a(n) does not exist; however, Limit a(n)^(1/n) = sqrt(5) (conjecture).

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..500

V. Kotesovec, Asymptotic of sequence A084611, Jul 26 2013

MATHEMATICA

Table[Sum[Abs[Coefficient[Expand[(1+x-x^2)^n], x, k]], {k, 0, 2*n}], {n, 0, 30}] (* Vaclav Kotesovec, Jul 28 2013 *)

PROG

(PARI) {a(n)=sum(k=0, 2*n, abs(polcoeff((1+x-x^2+x*O(x^k))^n, k)))}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A002426, A084600-A084610, A084612-A084615.

Sequence in context: A152981 A112040 A222187 * A078454 A023212 A106952

Adjacent sequences:  A084608 A084609 A084610 * A084612 A084613 A084614

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 01 2003

STATUS

approved

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Last modified August 25 13:50 EDT 2019. Contains 326324 sequences. (Running on oeis4.)