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 A096823 #8 Jun 03 2025 01:02:01 %S A096823 6,20,12,151115727449904501489664,56,40,24,272,1504,208,176,1312,112, %T A096823 80,48,6208,992,928,2059264,5696,736,144115176533131264,608,544,5056, %U A096823 416,352,4672,224,160,96,24704,24448,3904,3776,487936,112384,3392,22912 %N A096823 a(n) = p*(p+(2n-1))/2, where p = A096822(n) is the smallest primes of form 2^x-(2n-1). %C A096823 These numbers are clearly analogous to perfect numbers. %C A096823 sigma(a(n)) mod a(n) = 2*n. %e A096823 a(1) = 6 is the first even perfect number; %e A096823 a(7) = 24 corresponds to A096821(1) = 24; %e A096823 a(4) = 151115727449904501489664 = 2^38*(2^39-7) = 274877906944*549755813881; %Y A096823 Cf. A096502, A096821, A096822. %K A096823 nonn %O A096823 1,1 %A A096823 _Labos Elemer_, Jul 13 2004 %E A096823 Edited by _Max Alekseyev_, May 29 2025