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 A175875 #30 Aug 19 2025 17:59:56 %S A175875 3,30237,292317,3116957,4044037,6902277,73442597,115767957,137410557, %T A175875 416776357,526908197,541579497,695350653,758403357,1105731897, %U A175875 1178082357,1233277917,1309742557,1866261597,1998267037,2161411557,2563416237,2750761437,2873771997,2892203997,3331848517,3621735037,3758847117 %N A175875 Numbers k such that sigma(k+3) = 3*sigma(k). %C A175875 a(1) = A175874(3). %H A175875 Giovanni Resta, <a href="/A175875/b175875.txt">Table of n, a(n) for n = 1..180</a> (terms < 10^12) %o A175875 (PARI) isok(n) = sigma(n+3) == 3*sigma(n); \\ _Michel Marcus_, Oct 19 2013 %o A175875 (Magma) [n: n in [1..10^8] | SumOfDivisors(n+3) eq 3*SumOfDivisors(n)]; // _Vincenzo Librandi_, Jul 28 2017 %Y A175875 Cf. A000203, A002961, A175874, A272027 (3*sigma(n)). %K A175875 nonn %O A175875 1,1 %A A175875 _Zak Seidov_, Oct 06 2010 %E A175875 a(8)-a(21) from _Donovan Johnson_, Oct 11 2010 %E A175875 a(22)-a(24) from _Donovan Johnson_, Sep 10 2012 %E A175875 a(25) from _Zak Seidov_, Jul 07 2013 %E A175875 a(26)-a(28) from _Chai Wah Wu_, Jul 27 2017