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%I #12 Dec 26 2023 10:22:16
%S 121,161172,2358108863,379752191692104,672750374684751701305,
%T 13109994864250305051813161676,2810243697916419649311518955166566527,
%U 6626407610546884801816680266380777080570215568
%N Sum 11^((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="/A178192/b178192.txt">Table of n, a(n) for n = 1..40</a>
%t aa = {}; m = 11; sum = 0; Do[sum = sum + m^((n + 3) n/2); AppendTo[aa, sum], {n, 1, 20}]; aa (*Artur Jasinski*)
%t Table[11^((k^2+3k)/2),{k,10}]//Accumulate (* _Harvey P. Dale_, Apr 02 2020 *)
%o (PARI) a(n) = sum(k=1, n, 11^((k^2+3*k)/2)); \\ _Michel Marcus_, Sep 09 2013
%Y Cf. A178184-A178193.
%K nonn
%O 1,1
%A _Artur Jasinski_, May 21 2010