A071872 - OEIS

%I #12 Aug 20 2024 22:43:30

%S 0,2,1,1,3,2,4,3,3,3,5,4,6,5,7,6,6,6,6,6,6,6,8,7,9,8,10,11,10,10,10,

%T 10,12,11,13,12,12,12,14,13,15,14,14,14,14,14,16,15,15,15,15,15,15,15,

%U 15,15,17,16,18,17,19,18,20,19,19,19,19,19,19,19,19,19,21,20,22,23,22,22

%N Number of positive k such that k*tau(k) < n plus the number of positive k such that k*tau(k) = n-1.

%C For n > 80, does always a(n) > pi(n) the primes counting function ?

%o (PARI) for(n=1,100,print1(sum(i=1,n,if(sign(n-i*numdiv(i))-1,0,1))+sum(i=1,n,if(n-i*numdiv(i)-1,0,1)),","))

%Y Cf. A000005, A000720.

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Jun 09 2002

%E Name corrected by _Sean A. Irvine_, Aug 20 2024