A035004 - OEIS

%I #24 Nov 17 2021 15:56:58

%S 1,3,4,4,3,4,6,4,4,5,6,6,4,4,8,3,4,4,6,8,6,4,4,4,9,4,4,8,8,6,6,4,10,3,

%T 6,4,6,8,4,8,4,4,12,4,6,7,4,8,6,4,8,12,4,6,6,4,8,10,5,4,12,4,4,4,8,12,

%U 4,6,4,4,4,12,6,6,9,8,8,8,4,12,8,4,10,8,4,6,6,4,4,16,3,4,4,6,4,12,8,4

%N Number of divisors of the n-th nonprime.

%C a(n+1) = a(n) only when a(n) is even. Will these repeat terms include each even integer >= 4? (See also A075036.) - _Bill McEachen_, Nov 16 2021

%H Harvey P. Dale, <a href="/A035004/b035004.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A000005(A018252(n)). - _Omar E. Pol_, Jan 31 2013

%t DivisorSigma[0,Select[Range[200],!PrimeQ[#]&]] (* _Harvey P. Dale_, Mar 07 2016 *)

%o (PARI) for(n=1,33, if(!isprime(n), print1(numdiv(n), ", "))) \\ edited by _Michel Marcus_, Jan 04 2016

%Y Cf. A000005, A002808, A018252, A075036.

%K easy,nonn

%O 1,2

%A _Jason Earls_, Jul 05 2001

%E More terms from _Lior Manor_, Aug 16 2001