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 A102382 #14 Oct 02 2024 09:18:40 %S A102382 0,1,1,1,1,1,2,1,2,2,1,2,2,2,2,3,2,1,4,3,4,4,4,3,1,4,4,5,2,2,2,3,3,3, %T A102382 2,2,3,1,2,5,4,4,3,4,4,1,4,2,4,4,3,3,3,4,2,1,3,3,4,6,5,2,4,4,4,2,3,5, %U A102382 5,3,1,6,4,3,4,6,3,1,4,4,4,5,4,4,3,2,2,3,3,3,6,3,4,4,3,4,4,4,3,8,3,4,5,3,4 %N A102382 a(n) = A001221(A004094(n)). %e A102382 n = 19: reverse(2^19) = 882425 = 5^2*47*751, so a(19) = 3. %e A102382 n = 38: reverse(2^38) = 449609778472 = 2^3*56201222309, so a(38) = 2. - _Sean A. Irvine_, Sep 26 2023 %t A102382 a[n_] := PrimeNu[IntegerReverse[2^n]]; Array[a, 100, 0] (* _Amiram Eldar_, Oct 02 2024 *) %o A102382 (PARI) a(n) = omega(fromdigits(Vecrev(digits(2^n)))); \\ _Amiram Eldar_, Oct 02 2024 %Y A102382 Cf. A001221, A004094, A102383, A102384, A102385. %K A102382 nonn,base %O A102382 0,7 %A A102382 _Reinhard Zumkeller_, Jan 06 2005 %E A102382 a(38) corrected by _Sean A. Irvine_, Sep 26 2023