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A237647 G.f. satisfies: A(x) = (1 + x + x^2)^7 * A(x^2)^4. 3
1, 7, 56, 273, 1463, 6048, 26537, 97903, 377384, 1281497, 4502463, 14322560, 46849089, 141332583, 436556440, 1259742225, 3710541975, 10308494560, 29165172617, 78396244591, 214217633672, 559335671353, 1482519853311, 3772127020032, 9731443674113, 24191903115079, 60918829766648 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..26.

FORMULA

The odd-indexed bisection of A237646.

The 7th self-convolution of A237648.

G.f. A(x) satisfies:

(1) A(x) = Product_{n>=0} ( 1 + x^(2^n) + x^(2*2^n) )^(7*4^n).

(2) A(x) / A(-x) = (1+x+x^2)^7 / (1-x+x^2)^7.

EXAMPLE

G.f.: A(x) = 1 + 7*x + 56*x^2 + 273*x^3 + 1463*x^4 + 6048*x^5 + 26537*x^6 +...

where:

A(x) = (1+x+x^2)^7 * (1+x^2+x^4)^28 * (1+x^4+x^8)^112 * (1+x^8+x^16)^448 * (1+x^16+x^32)^896 *...* (1 + x^(2^n) + x^(2*2^n))^(7*4^n) *...

PROG

(PARI) {a(n)=local(A=1+x); for(i=1, #binary(n), A=(1+x+x^2)^7*subst(A^4, x, x^2) +x*O(x^n)); polcoeff(A, n)}

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

(PARI) {a(n)=local(A=1+x); A=prod(k=0, #binary(n), (1+x^(2^k)+x^(2*2^k)+x*O(x^n))^(7*4^k)); polcoeff(A, n)}

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

CROSSREFS

Cf. A237646, A237648, A237650.

Sequence in context: A153797 A244727 A090224 * A047664 A055345 A180287

Adjacent sequences:  A237644 A237645 A237646 * A237648 A237649 A237650

KEYWORD

nonn

AUTHOR

Paul D. Hanna, May 04 2014

STATUS

approved

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Last modified January 23 03:15 EST 2022. Contains 350504 sequences. (Running on oeis4.)