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 A078317 #12 Apr 10 2025 06:53:17 %S A078317 2,2,4,3,4,2,6,2,6,2,4,2,8,2,4,4,8,2,4,4,8,4,8,4,12,2,4,4,4,4,8,4,8,4, %T A078317 4,4,8,6,4,2,6,4,12,8,9,4,16,3,8,4,4,8,8,6,8,4,16,4,4,2,4,4,6,4,4,2,8, %U A078317 6,4,6,4,2,16,2,4,8,8,4,4,6,6,6,16,2,4,4,8,4,8,4,8,8,12,2,4,2,8,2,12,8 %N A078317 Number of divisors of n*rad(n)+1, where rad = A007947 (squarefree kernel). %H A078317 Reinhard Zumkeller, <a href="/A078317/b078317.txt">Table of n, a(n) for n = 1..10000</a> %F A078317 a(n) = A000005(A078310(n)). %t A078317 a[n_] := DivisorSigma[0, 1 + n * Times @@ FactorInteger[n][[;;, 1]]]; Array[a, 100] (* _Amiram Eldar_, Apr 10 2025 *) %o A078317 (Haskell) %o A078317 a078317 = a000005 . a078310 -- _Reinhard Zumkeller_, Jul 23 2013 %o A078317 (PARI) a(n) = numdiv(1 + n * vecprod(factor(n)[, 1])); \\ _Amiram Eldar_, Apr 10 2025 %Y A078317 Cf. A000005, A007947, A078310, A078313, A078314, A078318. %K A078317 nonn,easy %O A078317 1,1 %A A078317 _Reinhard Zumkeller_, Nov 23 2002