OFFSET
1,2
COMMENTS
Series of the kind m^((k^2+3k)/2) from k=1 to n was studied by Bernoulli and Euler.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..60
MATHEMATICA
aa = {}; m = 1/3; sum = 0; Do[sum = sum + m^((n + 3) n/2); AppendTo[aa, Numerator[sum]], {n, 1, 20}]; aa (*Artur Jasinski*)
Accumulate[Table[(1/3)^((k^2+3k)/2), {k, 20}]]//Numerator (* Harvey P. Dale, May 29 2020 *)
PROG
(PARI) a(n) = numerator(sum(k=1, n, (1/3)^((k^2+3*k)/2))); \\ Michel Marcus, Sep 09 2013
CROSSREFS
KEYWORD
frac,nonn
AUTHOR
Artur Jasinski, May 21 2010
STATUS
approved