This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A172296 #8 Jul 22 2025 04:07:17
%S A172296 3,8,15,26,39,56,75,98,129,172,233,312,413,540,707,898,1097,1410,1757,
%T A172296 2458,4167,6784,10323,16130,26631,37322,48601,60992,75471,118208,
%U A172296 201547,296916,414155,541186,680123,821202,1088219,1358206,1732527,2718718,6750117
%N A172296 Partial sums of Wagstaff numbers A000978.
%C A172296 The prime partial sums of Wagstaff numbers begin 3, 233, 1097, 201547, 680123. None of these but 3 is itself a Wagstaff number.
%F A172296 a(n) = Sum_{i=1..n} {integers i such that (2^i + 1)/3 is prime}.
%e A172296 a(4) = 3 + 5 + 7 + 11 = 26.
%Y A172296 Cf. A000040, A000978.
%K A172296 hard,nonn
%O A172296 1,1
%A A172296 _Jonathan Vos Post_, Jan 30 2010
%E A172296 a(41) added from the data at A000978 by _Amiram Eldar_, Jul 22 2025