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A251572 G.f. satisfies: A(x) = A(x^2 + x^3)/(1-x). 4
1, 1, 2, 3, 5, 9, 14, 23, 37, 60, 99, 164, 273, 447, 725, 1175, 1905, 3090, 5005, 8100, 13110, 21235, 34450, 55990, 91150, 148594, 242509, 396088, 647037, 1056355, 1722521, 2804571, 4559567, 7403398, 12009445, 19468381, 31546891, 51106662, 82782628, 134079950, 217147150, 351642635 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

What is the limit of a(n+1)/a(n) ?  Seems to be near (sqrt(5)+1)/2 ...

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..4150

Vaclav Kotesovec, Graph - a(n+1)/a(n)

FORMULA

G.f. satisfies: A(x) = A(x^4 + 2*x^5 + 2*x^6 + 3*x^7 + 3*x^8 + x^9) / ((1-x)*(1-x^2-x^3)).

G.f.: 1/Product_{n>=0} (1 - G(x,n)) where G(x,n+1) = G(x^2+x^3,n) with G(x,0)=x.

EXAMPLE

G.f.: A(x) = 1 + x + 2*x^2 + 3*x^3 + 5*x^4 + 9*x^5 + 14*x^6 + 23*x^7 +...

such that A(x) = A(x^2 + x^3)/(1-x), where:

A(x^2+x^3) = 1 + x^2 + x^3 + 2*x^4 + 4*x^5 + 5*x^6 + 9*x^7 + 14*x^8 +

23*x^9 + 39*x^10 + 65*x^11 + 109*x^12 + 174*x^13 + 278*x^14 +...

G.f. equals an infinite product involving iterations of x^2+x^3:

A(x) = 1 / ( (1-x) * (1 - (x^2+x^3)) * (1 - (x^4 + 2*x^5 + 2*x^6 + 3*x^7 + 3*x^8 + x^9)) *...* (1 - G(x,n)) *...)

where G(x,n+1) = G(x^2+x^3,n) with G(x,0) = x.

Iterations of x^2+x^3 begin:

G(x,1) = x^2 + x^3;

G(x,2) = x^4 + 2*x^5 + 2*x^6 + 3*x^7 + 3*x^8 + x^9;

G(x,3) = x^8 + 4*x^9 + 8*x^10 + 14*x^11 + 23*x^12 + 32*x^13 + 43*x^14 + 63*x^15 + 96*x^16 + 141*x^17 + 192*x^18 + 240*x^19 + 267*x^20 + 255*x^21 + 210*x^22 + 150*x^23 + 87*x^24 + 36*x^25 + 9*x^26 + x^27;

...

PROG

(PARI) {a(n)=local(A=1+x); for(i=1, #binary(n)+1, A=subst(A, x, x^2+x^3)/(1-x +x*O(x^n))); polcoeff(A, n)}

for(n=0, 50, print1(a(n), ", "))

CROSSREFS

Cf. A251581, A251582.

Sequence in context: A244986 A293547 A124502 * A173714 A026746 A004699

Adjacent sequences:  A251569 A251570 A251571 * A251573 A251574 A251575

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jan 23 2015

STATUS

approved

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Last modified April 26 12:31 EDT 2019. Contains 322472 sequences. (Running on oeis4.)