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A245768 G.f. satisfies: A(x) = 1 + x*A(x)^4 / (A(x) - x*A'(x)). 1
1, 1, 4, 26, 224, 2337, 28088, 377144, 5544824, 88039724, 1494960308, 26954440490, 513267546824, 10279486681982, 215822203235952, 4737785187211908, 108509135362455192, 2588049036893027820, 64180886929824389840, 1652564046132761428040, 44124859215715377422552, 1220338620776444854394561 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..21.

FORMULA

G.f. A(x) satisfies:

(1) [x^n] A(x)^(n+1) = (n+1) * [x^(n-1)] A(x)^(n+3) for n>=1.

(2) A(x) = x/Series_Reversion(G(x)) where G(x) = x*G(x)^4 + x^2*G(x)^3*G'(x).

EXAMPLE

G.f.: A(x) = 1 + x + 4*x^2 + 26*x^3 + 224*x^4 + 2337*x^5 + 28088*x^6 +...

The table of coefficients of x^k in A(x)^n begin:

n=1: [1,  1,  4,  26,  224,  2337,  28088,   377144, ...];

n=2: [1,  2,  9,  60,  516,  5330,  63318,   840808, ...];

n=3: [1,  3, 15, 103,  888,  9105, 107050,  1406655, ...];

n=4: [1,  4, 22, 156, 1353, 13804, 160844,  2092748, ...];

n=5: [1,  5, 30, 220, 1925, 19586, 226480,  2919840, ...];

n=6: [1,  6, 39, 296, 2619, 26628, 305979,  3911688, ...];

n=7: [1,  7, 49, 385, 3451, 35126, 401625,  5095392, ...];

n=8: [1,  8, 60, 488, 4438, 45296, 515988,  6501760, ...];

n=9: [1,  9, 72, 606, 5598, 57375, 651948,  8165700, ...];

n=10:[1, 10, 85, 740, 6950, 71622, 812720, 10126640, ...]; ...

in which the diagonals illustrate the relation

[x^n] A(x)^(n+1) = (n+1) * [x^(n-1)] A(x)^(n+3) for n>=1

as follows:

[x^1] A(x)^2 = 2 = 2*[x^0] A(x)^4 = 2*1 ;

[x^2] A(x)^3 = 15 = 3*[x^1] A(x)^5 = 3*5 ;

[x^3] A(x)^4 = 156 = 4*[x^2] A(x)^6 = 4*39 ;

[x^4] A(x)^5 = 1925 = 5*[x^3] A(x)^7 = 5*385 ;

[x^5] A(x)^6 = 26628 = 6*[x^4] A(x)^8 = 6*4438 ;

[x^6] A(x)^7 = 401625 = 7*[x^5] A(x)^9 = 7*57375 ;

[x^7] A(x)^8 = 6501760 = 8*[x^6] A(x)^10 = 8*812720 ; ...

Also, from the above table, we can generate:

[1/1, 2/2, 15/3, 156/4, 1925/5, 26628/6, 401625/7, 812720/8, ...]

= [1, 1, 5, 39, 385, 4438, 57375, 812720, 12428977, 203183595, ...];

the g.f. G(x) of which begins:

G(x) = x + x^2 + 5*x^3 + 39*x^4 + 385*x^5 + 4438*x^6 + 57375*x^7 +...

such that:

G(x) = x*G(x)^4 + x^2*G(x)^3*G'(x) and G(x) = A(G(x)).

PROG

(PARI) /* From [x^n] A(x)^(n+1) = (n+1) * [x^(n-1)] A(x)^(n+3): */

{a(n)=local(A=[1, 1]); for(i=2, n, A=concat(A, 0); A[#A]=((#A)*Vec(Ser(A)^(#A+2))[#A-1]-Vec(Ser(A)^(#A))[#A])/(#A)); A[n+1]}

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

(PARI) /* From A(x) = 1 +  x*A(x)^4 / (A(x) - x*A'(x)): */

{a(n)=local(A=1+x); for(i=1, n, A = 1 + x*A^4/(A - x*A' +x*O(x^n))); polcoeff(A, n)}

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

(PARI) /* From A(x) = x/Series_Reversion(G) where G = x*G^4 + x^2*G^3*G': */

{a(n)=local(G=1+x); for(i=1, n, G = 1 + x*G^4 + x^2*G^3*G' +x*O(x^n)); polcoeff(x/serreverse(x*G +x^2*O(x^n)), n)}

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

CROSSREFS

Cf. A088715, A245118.

Sequence in context: A219780 A259902 A089816 * A152407 A291847 A168448

Adjacent sequences:  A245765 A245766 A245767 * A245769 A245770 A245771

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Aug 01 2014

STATUS

approved

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Last modified January 28 12:58 EST 2020. Contains 331321 sequences. (Running on oeis4.)