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 A238746 #16 Jan 21 2024 02:23:33 %S A238746 1,2,3,3,4,5,5,7,4,6,6,9,7,7,9,11,10,8,12,9,13,5,10,13,9,15,14,15,9, %T A238746 14,16,10,18,19,17,13,18,10,19,11,16,21,12,15,24,19,17,22,16,22,12,23, %U A238746 24,6,19,20,29,21,21,26,22,25,13,30,27,11,26,25,19,34 %N A238746 Number of distinct prime signatures that occur among the divisors of the n-th prime signature number (A025487(n)). %C A238746 Also the number of members of A025487 that divide A025487(n). %H A238746 Amiram Eldar, <a href="/A238746/b238746.txt">Table of n, a(n) for n = 1..10000</a> %F A238746 a(n) = A085082(A025487(n)) = A085082(A181822(n)). %F A238746 a(n) = A322584(A025487(n)). - _Amiram Eldar_, Jan 21 2024 %e A238746 5 members of A025487 divide A025487(6) = 12 (namely, 1, 2, 4, 6 and 12); therefore, a(6) = 5. %t A238746 lpsQ[n_] := n == 1 || (Max@ Differences[(f = FactorInteger[n])[[;;,2]]] < 1 && f[[-1, 1]] == Prime[Length[f]]); lps = Select[Range[6000], lpsQ]; c[n_] := Count[Divisors[n], _?(MemberQ[lps, #] &)]; c /@ lps (* _Amiram Eldar_, Jan 21 2024 *) %Y A238746 Cf. A085082, A025487, A181822, A322584. %Y A238746 Rearrangement of A115728, A115729 and A238690. %Y A238746 A116473(n) is the number of times n appears in the sequence. %K A238746 nonn %O A238746 1,2 %A A238746 _Matthew Vandermast_, Apr 28 2014