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A213252 G.f. satisfies: A(x) = 1 + x/A(-x)^2. 4
1, 1, 2, -1, -10, 7, 88, -68, -946, 767, 11298, -9425, -144024, 122436, 1919440, -1653776, -26419778, 22992655, 372670246, -326863667, -5358911450, 4729547023, 78264621664, -69424933968, -1157715304760, 1031309398852, 17309542787288, -15474833826028 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Paul D. Hanna, Table of n, a(n) for n = 0..200

FORMULA

G.f. satisfies: A(x) = G(x/A(x)^2) where G(x) = A(x*G(x)^2) is the g.f. of A006319 (royal paths in a lattice).

G.f. satisfies: A(x) = sqrt( x/Series_Reversion( x*C(x/(1-x)^2)^2 ) ) where C(x) = 1 + x*C(x)^2 = (1-sqrt(1-4*x))/(2*x) is the g.f. of the Catalan numbers (A000108).

G.f. satisfies: A(x) = A(x)*A(-x) + x/A(x).

EXAMPLE

G.f.: A(x) = 1 + x + 2*x^2 - x^3 - 10*x^4 + 7*x^5 + 88*x^6 - 68*x^7 +...

where

x/A(-x)^2 = x + 2*x^2 - x^3 - 10*x^4 + 7*x^5 + 88*x^6 - 68*x^7 +...

A(x)^2 = 1 + 2*x + 5*x^2 + 2*x^3 - 18*x^4 - 10*x^5 + 151*x^6 + 88*x^7 +...

The g.f. G(x) of A006319 begins:

G(x) = 1 + x + 4*x^2 + 16*x^3 + 68*x^4 + 304*x^5 + 1412*x^6 + 6752*x^7 +...

where G(x) = A(x*G(x)^2) and G(x/A(x)^2) = A(x);

also, G(x) = F(x/(1-x)^2) where F(x) = 1 + x*F(x)^2 is g.f. of A000108:

F(x) = 1 + x + 2*x^2 + 5*x^3 + 14*x^4 + 42*x^5 + 132*x^6 + 429*x^7 +...

PROG

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

for(n=0, 40, print1(a(n), ", "))

CROSSREFS

Cf. A006319, A213281, A213335, A143045; A000108.

Sequence in context: A324246 A225470 A081099 * A122017 A219900 A136233

Adjacent sequences:  A213249 A213250 A213251 * A213253 A213254 A213255

KEYWORD

sign

AUTHOR

Paul D. Hanna, Jun 07 2012

STATUS

approved

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Last modified February 19 00:35 EST 2020. Contains 332028 sequences. (Running on oeis4.)