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A317798 G.f.: Sum_{n>=0} (3*(1+x)^n - 1)^n / 3^(n+1). 1
1, 15, 786, 69261, 8554530, 1359020643, 263929299177, 60582032629791, 16046282916588207, 4817035600778756553, 1616224504900354928832, 599373591433178971787007, 243449152911402772344286998, 107482020677618238226506065235, 51249638236281451846248205583562, 26247197050200652206165329786055981, 14369481728948627418149559363836673273 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

FORMULA

G.f. satisfies:

(1) Sum_{n>=0} 3^n * (1+x)^(n^2) / (3 + (1+x)^n)^(n+1).

(2) Sum_{n>=0} ((1+x)^n - 1/3)^n / 3.

EXAMPLE

G.f.: A(x) = 1 + 15*x + 786*x^2 + 69261*x^3 + 8554530*x^4 + 1359020643*x^5 + 263929299177*x^6 + 60582032629791*x^7 + 16046282916588207*x^8 + ...

such that

A(x) = 1/3  +  (3*(1+x) - 1)/3^2  +  (3*(1+x)^2 - 1)^3/3^3  +  (3*(1+x)^3 - 1)^3/3^4  +  (3*(1+x)^4 - 1)^4/3^5  +  (3*(1+x)^5 - 1)^5/3^6  + ...

Also,

A(x) = 1/4  +  3*(1+x)/(3 + (1+x))^2  +  3^2*(1+x)^4/(3 + (1+x)^2)^3  +  3^3*(1+x)^9/(3 + (1+x)^3)^4  +  3^4*(1+x)^16/(3 + (1+x)^4)^5  +  3^5*(1+x)^25/(3 + (1+x)^5)^6  +  3^6*(1+x)^36/(3 + (1+x)^6)^7  + ...

CROSSREFS

Cf. A122400, A301463, A317799, A301582.

Sequence in context: A333562 A116094 A267754 * A280310 A211104 A279493

Adjacent sequences:  A317795 A317796 A317797 * A317799 A317800 A317801

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Aug 14 2018

STATUS

approved

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Last modified January 28 18:56 EST 2022. Contains 350657 sequences. (Running on oeis4.)