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 A079083 #14 Apr 07 2025 09:51:37 %S A079083 3,3,3,3,3,3,3,3,3,3,19,3,3,3,3,3,3,17,3,3,5,3,3,3,3,3,3,3,3,3,3,3,3, %T A079083 3,3,19,41,3,3,3,3,3,3,3,3,5,7,3,3,3,3,3,3,3,3,3,3,17,3,3,3,3,3,3,3,3, %U A079083 13,3,3,3,3,3,11,5,3,3,3,3,3,3,3,3,3,5,3,3,3,3,3,3,3,3,3,3,3,3,3,3,131,137 %N A079083 Smallest odd prime factor of (prime(n)+1)*(prime(n+1)+1)/4. %H A079083 Reinhard Zumkeller, <a href="/A079083/b079083.txt">Table of n, a(n) for n = 1..10000</a> %F A079083 a(n) = A078701(A079079(n)). %t A079083 odd[n_] := n / 2^IntegerExponent[n, 2]; a[n_] := FactorInteger[odd[(Prime[n]+1)*(Prime[n+1]+1)]][[1, 1]]; Array[a, 100] (* _Amiram Eldar_, Apr 06 2025 *) %o A079083 (Haskell) %o A079083 a079083 = a078701 . a079079 -- _Reinhard Zumkeller_, Oct 08 2012 %o A079083 (PARI) odd(n) = n >> valuation(n, 2); %o A079083 a(n) = factor(odd((prime(n)+1)*(prime(n+1)+1)))[1, 1]; \\ _Amiram Eldar_, Apr 06 2025 %Y A079083 Cf. A078701, A079079, A079084. %K A079083 nonn %O A079083 1,1 %A A079083 _Reinhard Zumkeller_, Dec 22 2002