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A120601 G.f. satisfies: 15*A(x) = 14 + 27*x + A(x)^6, starting with [1,3,15]. 2
1, 3, 15, 210, 3510, 65562, 1310901, 27446760, 594104940, 13187589690, 298555767279, 6867021319722, 160017552201780, 3769622456958720, 89628027015591870, 2148034269252052608, 51836638064282565579 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

See comments in A120588 for conditions needed for an integer sequence to satisfy a functional equation of the form: r*A(x) = c + b*x + A(x)^n.

LINKS

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

FORMULA

G.f.: A(x) = 1 + Series_Reversion((1+15*x - (1+x)^6)/27). Lagrange Inversion yields: G.f.: A(x) = Sum_{n>=0} C(6*n,n)/(5*n+1) * (14+27*x)^(5*n+1)/15^(6*n+1). - Paul D. Hanna, Jan 24 2008

a(n) ~ 3^(-1/2 + 3*n) * (-14 + 5*(5/2)^(6/5))^(1/2 - n) / (2^(3/5) * 5^(9/10) * n^(3/2) * sqrt(Pi)). - Vaclav Kotesovec, Nov 28 2017

EXAMPLE

A(x) = 1 + 3*x + 15*x^2 + 210*x^3 + 3510*x^4 + 65562*x^5 +...

A(x)^6 = 1 + 18*x + 225*x^2 + 3150*x^3 + 52650*x^4 + 983430*x^5 +...

MATHEMATICA

CoefficientList[1 + InverseSeries[Series[(1+15*x - (1+x)^6)/27, {x, 0, 20}], x], x] (* Vaclav Kotesovec, Nov 28 2017 *)

PROG

(PARI) {a(n)=local(A=1+3*x+15*x^2+x*O(x^n)); for(i=0, n, A=A+(-15*A+14+27*x+A^6)/9); polcoeff(A, n)}

CROSSREFS

Cf. A120588 - A120600, A120602 - A120607.

Sequence in context: A195515 A003505 A270354 * A145272 A264705 A117820

Adjacent sequences:  A120598 A120599 A120600 * A120602 A120603 A120604

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 16 2006

STATUS

approved

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Last modified August 12 16:32 EDT 2022. Contains 356077 sequences. (Running on oeis4.)