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 A336105 #11 Sep 11 2020 11:46:15
%S A336105 1,1,1,2,1,3,1,6,2,6,2,60,1,6,6,24,1,120,1,360,12,24,2,2520,6,6,6,720,
%T A336105 6,2520,1,120,24,6,24,604800,2,6,24,20160,2,10080,6,5040,720,24,6,
%U A336105 1814400,2,5040,120,5040,6,15120,720,40320,24,720,2
%N A336105 Number of permutations of the prime indices of 2^n - 1.
%C A336105 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
%F A336105 a(n) = A008480(2^n - 1).
%F A336105 a(n) = A336104(n) + A335432(n).
%e A336105 The a(n) permutations for n = 2, 4, 6, 8, 21:
%e A336105 (2) (2,3) (2,2,4) (2,3,7) (31,4,4,68)
%e A336105 (3,2) (2,4,2) (2,7,3) (31,4,68,4)
%e A336105 (4,2,2) (3,2,7) (31,68,4,4)
%e A336105 (3,7,2) (4,31,4,68)
%e A336105 (7,2,3) (4,31,68,4)
%e A336105 (7,3,2) (4,4,31,68)
%e A336105 (4,4,68,31)
%e A336105 (4,68,31,4)
%e A336105 (4,68,4,31)
%e A336105 (68,31,4,4)
%e A336105 (68,4,31,4)
%e A336105 (68,4,4,31)
%t A336105 primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
%t A336105 Table[Length[Permutations[primeMS[2^n-1]]],{n,30}]
%Y A336105 A008480 is not restricted to predecessors of powers of 2.
%Y A336105 A325617 is the version for factorial numbers.
%Y A336105 A335489 counts strict permutations of prime indices.
%Y A336105 Cf. A056239, A112798, A335432, A336104.
%Y A336105 The numbers 2^n - 1: A000225, A046051, A046800, A046801, A049093, A325610, A325611, A325612, A325625.
%K A336105 nonn
%O A336105 1,4
%A A336105 _Gus Wiseman_, Sep 03 2020