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 A078312 #12 Apr 10 2025 05:24:26 %S A078312 2,5,5,3,13,37,5,17,7,101,61,73,17,197,113,11,29,109,181,67,17,97,53, %T A078312 29,7,677,41,131,421,53,37,13,109,89,613,31,137,17,761,401,29,353,37, %U A078312 19,13,73,17,17,43,167,1301,41,281,13,89,157,13,673,1741,1801,1861,769 %N A078312 Greatest prime factor of n*rad(n)+1, where rad = A007947 (squarefree kernel). %H A078312 Reinhard Zumkeller, <a href="/A078312/b078312.txt">Table of n, a(n) for n = 1..10000</a> %F A078312 a(n) = A006530(A078310(n)). %t A078312 a[n_] := FactorInteger[1 + n * Times @@ FactorInteger[n][[;;, 1]]][[-1, 1]]; Array[a, 100] (* _Amiram Eldar_, Apr 10 2025 *) %o A078312 (Haskell) %o A078312 a078312 = a006530 . a078310 -- _Reinhard Zumkeller_, Jul 23 2013 %o A078312 (PARI) a(n) = my(f = factor(1 + n * vecprod(factor(n)[, 1]))); f[#f~, 1]; \\ _Amiram Eldar_, Apr 10 2025 %Y A078312 Cf. A006530, A007947, A078310, A078311. %K A078312 nonn,easy %O A078312 1,1 %A A078312 _Reinhard Zumkeller_, Nov 23 2002