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Search: id:A132317
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| A132317 |
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a(n) = [x^(2^n)] Product_{i=0..n} (1 + x^(2^i) )^(2^(n-i)); equals column 1 of triangle A132318. |
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+0
3
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| 1, 2, 15, 1024, 7048181, 469389728563470, 2954306864416502250656677496683, 165756604793755389851497802171770083459242616940095659925793836
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Next term, a(8), has 126 digits.
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EXAMPLE
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a(0) = [x] (1+x) = 1;
a(1) = [x^2] (1+x)^2*(1+x^2) = 2;
a(2) = [x^4] (1+x)^4*(1+x^2)^2*(1+x^4) = 15;
a(3) = [x^8] (1+x)^8*(1+x^2)^4*(1+x^4)^2*(1+x^8) = 1024;
a(4) = [x^16] (1+x)^16*(1+x^2)^8*(1+x^4)^4*(1+x^8)^2*(1+x^16) = 7048181.
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PROGRAM
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(PARI) {a(n)=polcoeff(prod(i=0, n, (1 + x^(2^i) +x*O(x^(2^n)))^(2^(n-i))), 2^n)}
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CROSSREFS
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Cf. A132318, A132316.
Sequence in context: A007542 A090604 A007467 this_sequence A068409 A096232 A064171
Adjacent sequences: A132314 A132315 A132316 this_sequence A132318 A132319 A132320
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Aug 19 2007
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