A178191 - OEIS

%I #10 Jul 21 2016 17:14:50

%S 1,344,825945,13881657616,1633163136864785,1344980069223035633256,

%T 7753542448037025041629822057,312883404805904029979088478768109600,

%U 88381817680515537538446482833052972519290401

%N Numerators of sum (1/7)^((k^2+3k)/2) from k=1 to n.

%C Series of the kind m^((k^2+3k)/2) from k=1 to n was studied by Bernoulli and Euler.

%H Vincenzo Librandi, <a href="/A178191/b178191.txt">Table of n, a(n) for n = 1..45</a>

%t aa = {}; m = 1/7; sum = 0; Do[sum = sum + m^((n + 3) n/2); AppendTo[aa, Numerator[sum]], {n, 1, 20}]; aa (*Artur Jasinski*)

%t Numerator[Accumulate[Table[(1/7)^((n^2+3n)/2),{n,10}]]] (* _Harvey P. Dale_, Jul 21 2016 *)

%o (PARI) a(n) = numerator(sum(k=1, n, (1/7)^((k^2+3*k)/2))); \\ _Michel Marcus_, Sep 09 2013

%Y Cf. A178184-A178193.

%K frac,nonn

%O 1,2

%A _Artur Jasinski_, May 21 2010