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 A015945 #17 Mar 25 2021 12:39:38 %S A015945 2,10,50,250,410,1250,2050,5050,6250,10250,16810,25250,31250,51250, %T A015945 84050,126250,156250,207050,256250,336610,405050,420250,510050,631250, %U A015945 689210,781250,1035250,1281250,1683050,1750250,2025250,2101250,2550250,3156250,3446050 %N A015945 Positive integers n such that n | (2^n + n/2 + 1). %F A015945 a(n) = 2 * A015950(n). - _Max Alekseyev_, Aug 04 2011 %o A015945 (Python) %o A015945 A015945_list = [n for n in range(2,10**6,2) if pow(2,n,n) == n//2-1] # _Chai Wah Wu_, Mar 25 2021 %K A015945 nonn %O A015945 1,1 %A A015945 _Robert G. Wilson v_