cp's OEIS Frontend

A211932 a(n) = Sum_{ m=1..n and gcd(n,m)>1 } tau(m), where tau is the number of divisors function, A000005.

%I A211932 #28 Jan 22 2025 11:40:10
%S A211932 0,2,2,5,2,11,2,13,9,19,2,28,2,29,25,32,2,47,2,50,35,50,2,69,19,62,41,
%T A211932 72,2,96,2,80,59,86,47,114,2,99,72,118,2,144,2,125,107,125,2,164,31,
%U A211932 158,100,151,2,188,71,174,112,167,2,229,2,183,151,188,87,247,2,208,142,252,2,271,2,228,203,238,85
%N A211932 a(n) = Sum_{ m=1..n and gcd(n,m)>1 } tau(m), where tau is the number of divisors function, A000005.
%H A211932 Antti Karttunen, <a href="/A211932/b211932.txt">Table of n, a(n) for n = 1..20000</a>
%F A211932 a(n) = A006218(n) - A143615(n).
%p A211932 A211932 := proc(n)
%p A211932         local a,m;
%p A211932         a := 0 ;
%p A211932         for m from 1 to n do
%p A211932                 if gcd(m,n) > 1 then
%p A211932                 a := a+numtheory[tau](m) ;
%p A211932                 end if;
%p A211932         end do:
%p A211932         a ;
%p A211932 end proc: # _R. J. Mathar_, Aug 08 2012
%o A211932 (PARI) A211932(n) = sum(m=1,n,if(1==gcd(n,m),0,numdiv(m))); \\ _Antti Karttunen_, Jan 22 2025
%Y A211932 Cf. A000005, A143615.
%K A211932 nonn,easy
%O A211932 1,2
%A A211932 _Naohiro Nomoto_, Aug 05 2012