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 A163821 #5 Oct 16 2024 09:22:37 %S A163821 2,3,5,7,3,7,9,3,6,72,0,14,10,0,126,0,32,42,120,96,3888,324,6,1701,0, %T A163821 0,4032,1152,0,0,0,45360,12960,27440,23328,3024,0,102060,27216,0,0, %U A163821 97200,0,100800,158760,0,0,67200 %N A163821 a(n) = product of decimal digits of A000043(n). %F A163821 a(n) = A007954(A000043(n)). - _Amiram Eldar_, Oct 16 2024 %t A163821 a[n_] := Times @@ IntegerDigits[MersennePrimeExponent[n]]; Array[a, 48] (* _Amiram Eldar_, Oct 16 2024 *) %Y A163821 Cf. A000043, A007954. %K A163821 base,nonn,more %O A163821 1,1 %A A163821 Boris Hostnik (megpplus(AT)siol.net), Aug 04 2009 %E A163821 a(38)-a(39) corrected and a(40)-a(48) added by _Amiram Eldar_, Oct 16 2024