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A317799
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G.f.: Sum_{n>=0} (4*(1+x)^n - 1)^n / 4^(n+1).
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1
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1, 28, 2644, 418108, 92624756, 26388012380, 9189259388052, 3782063138596476, 1796136011427955636, 966755321167565129372, 581573928178258915024596, 386690499153558305585430460, 281600848152507182372274325492, 222904650325844057584524049181660, 190559248618061561787517993382005012
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OFFSET
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0,2
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LINKS
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Table of n, a(n) for n=0..14.
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FORMULA
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G.f. satisfies:
(1) Sum_{n>=0} 4^n * (1+x)^(n^2) / (4 + (1+x)^n)^(n+1).
(2) Sum_{n>=0} ((1+x)^n - 1/4)^n / 4.
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EXAMPLE
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G.f.: A(x) = 1 + 28*x + 2644*x^2 + 418108*x^3 + 92624756*x^4 + 26388012380*x^5 + 9189259388052*x^6 + 3782063138596476*x^7 + 1796136011427955636*x^8 + ...
such that
A(x) = 1/4 + (4*(1+x) - 1)/4^2 + (4*(1+x)^2 - 1)^3/4^3 + (4*(1+x)^3 - 1)^4/4^4 + (4*(1+x)^4 - 1)^4/4^5 + (4*(1+x)^5 - 1)^5/4^6 + ...
Also,
A(x) = 1/5 + 4*(1+x)/(4 + (1+x))^2 + 4^2*(1+x)^4/(4 + (1+x)^2)^4 + 4^3*(1+x)^9/(4 + (1+x)^3)^4 + 4^4*(1+x)^16/(4 + (1+x)^4)^5 + 4^5*(1+x)^25/(4 + (1+x)^5)^6 + 4^6*(1+x)^36/(4 + (1+x)^6)^7 + ...
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CROSSREFS
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Cf. A122400, A301463, A317798, A301583.
Sequence in context: A281137 A100548 A103660 * A275654 A283519 A284770
Adjacent sequences: A317796 A317797 A317798 * A317800 A317801 A317802
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna, Aug 14 2018
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STATUS
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approved
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