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 A247787 #11 Sep 08 2022 08:46:09 %S A247787 4,6,13,14,32,31,48,38,78,80,62,74,121,108,128,192,182,133,160,192, %T A247787 180,158,288,240,194,272,252,288,256,403,288,390,448,278,480,352,314, %U A247787 434,494,576,576,381,512,576,528,398,422,540,608,458,768,702,532,672 %N A247787 Sum of divisors of 2*prime(n)-1. %C A247787 See A005382 (primes p such that sigma(2p-1) = 2p). %H A247787 Jens Kruse Andersen, <a href="/A247787/b247787.txt">Table of n, a(n) for n = 1..10000</a> %F A247787 a(n) = sigma(A076274(n)) = A000203(A076274(n)). %e A247787 For n = 3; prime(3) = 5, a(3) = sigma(2*5-1) = sigma(9) = 13. %o A247787 (Magma) [SumOfDivisors(2*p-1): p in PrimesUpTo(2000)] %o A247787 (PARI) vector(100,n,sigma(2*prime(n)-1)) \\ _Derek Orr_, Sep 25 2014 %Y A247787 Cf. A000203, A072057, A005382, A247788. %K A247787 nonn,easy %O A247787 1,1 %A A247787 _Jaroslav Krizek_, Sep 24 2014