%I #2 Mar 30 2012 17:27:02
%S 1,3,6,8,11,23,51,123,1451,165876,368310548,131319102413076,
%T 429434116256258636749076,5044128476605888967010031050325156534548,
%U 998085332225053172931293515663565518940387354129475684145085443611977451
%N Last terms in the groups defined in A160275.
%F a(n) = (sqrt(8*(A160275(1) + A160275(2) + ... + A160275(n)) + 1) - 1) / 2
%Y Cf. A160275, A160276, A075634, A079801.
%K nonn
%O 1,2
%A _Max Alekseyev_, May 08 2009