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 A087349 #13 Apr 10 2025 05:19:10 %S A087349 3,5,5,9,7,13,9,11,11,21,13,25,15,17,17,33,19,37,21,23,23,45,25,29,27, %T A087349 29,29,57,31,61,33,35,35,39,37,73,39,41,41,81,43,85,45,47,47,93,49,55, %U A087349 51,53,53,105,55,59,57,59,59,117,61,121,63,65,65,69,67,133,69,71,71 %N A087349 a(n) = n + (smallest prime-factor of n+1). %H A087349 Reinhard Zumkeller, <a href="/A087349/b087349.txt">Table of n, a(n) for n = 1..10000</a> %F A087349 a(n) = n + A020639(n+1). %F A087349 a(n) = A061228(n+1) - 1. %t A087349 a[n_] := n + FactorInteger[n+1][[1,1]]; Array[a, 100] (* _Amiram Eldar_, Apr 10 2025 *) %o A087349 (Haskell) %o A087349 a087349 n = a020639 (n + 1) + n -- _Reinhard Zumkeller_, Mar 31 2014 %o A087349 (PARI) a(n) = n + factor(n+1)[1,1]; \\ _Amiram Eldar_, Apr 10 2025 %Y A087349 Cf. A020639, A061228. %K A087349 nonn,easy %O A087349 1,1 %A A087349 _Reinhard Zumkeller_, Oct 20 2003