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 A078320 #13 Apr 10 2025 05:23:57 %S A078320 2,5,7,6,15,37,12,17,11,101,63,73,24,197,115,14,36,109,183,70,32,102, %T A078320 60,34,15,677,43,134,423,70,52,18,116,102,615,38,144,39,763,401,60, %U A078320 358,49,39,30,102,37,34,49,170,1303,55,288,23,108,162,30,678,1743,1801 %N A078320 Sum of all prime factors of n*rad(n)+1, where rad = A007947 (squarefree kernel). %H A078320 Reinhard Zumkeller, <a href="/A078320/b078320.txt">Table of n, a(n) for n = 1..10000</a> %F A078320 a(n) = A001414(A078310(n)). %t A078320 a[n_] := Plus @@ Times @@@ FactorInteger[1 + n * Times @@ FactorInteger[n][[;;, 1]]]; Array[a, 100] (* _Amiram Eldar_, Apr 10 2025 *) %o A078320 (PARI) rad(n)=my(f=factor(n)[,1]); prod(i=1,#f,f[i]) %o A078320 a(n)=my(f=factor(n*rad(n)+1));sum(i=1,#f~,f[i,1]*f[i,2]) \\ _Charles R Greathouse IV_, Jul 15 2013 %o A078320 (Haskell) %o A078320 a078320 = a001414 . a078310 -- _Reinhard Zumkeller_, Jul 23 2013 %Y A078320 Cf. A001414, A078310, A078314, A078318, A078319. %K A078320 nonn,easy %O A078320 1,1 %A A078320 _Reinhard Zumkeller_, Nov 23 2002