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Number of divisors of n-th refactorable number (A033950(n)).
7

%I #18 Sep 08 2022 08:44:53

%S 1,2,4,3,6,6,8,9,8,8,12,12,10,12,8,12,8,12,8,12,8,8,12,18,8,12,9,12,8,

%T 20,8,18,12,18,8,8,8,12,24,12,8,16,18,8,9,12,14,18,18,8,24,8,12,24,12,

%U 8,20,12,8,8,24,18,5,8,12,16,8,24,18,12,8,30,12,8,24,12,8,8,18,12,8,24,8

%N Number of divisors of n-th refactorable number (A033950(n)).

%C A number n is refactorable if the number of divisors of n divides n.

%H Amiram Eldar, <a href="/A039819/b039819.txt">Table of n, a(n) for n = 1..10000</a>

%F A033950(n)/a(n) = A036762(n).

%F a(n) = A000005(A033950(n)). - _Omar E. Pol_, Jan 17 2017

%t fQ[n_] := Mod[n, DivisorSigma[0, n]] == 0; DivisorSigma[0, # ] & /@ Select[ Range[1000], fQ[ # ] &] (* _Robert G. Wilson v_ *)

%o (Magma) v:=[ n: n in [1..900] | n mod NumberOfDivisors(n) eq 0 ]; [NumberOfDivisors(v[i]): i in [1..#v]]; // _Marius A. Burtea_, Jul 02 2019

%Y Cf. A033950, A000005, A036762, A281188.

%K nonn

%O 1,2

%A _N. J. A. Sloane_.

%E More terms from _Robert G. Wilson v_, Oct 29 2005

%E Minor edits by _Franklin T. Adams-Watters_, Jan 17 2017