A168048 - OEIS

%I #8 May 11 2019 01:34:37

%S 0,1,2,4,6,9,12,16,20,24,30,35,42,48,54,60,70,77,88,96,104,112,126,

%T 135,144,153,162,171,190,200,220,231,242,253,264,275,300,312,324,336,

%U 364,377,406,420,434,448,480,495,510,525,540,555,592,608,624,640,656,672

%N a(n) = C(n)*Pi(n) where C(n) = number of nonprimes <= n, Pi(n) = number of primes <= n.

%F a(n) = A062298(n)*A000720(n).

%p A000720 := proc(n) numtheory[pi](n) ; end proc: A168048 := proc(n) pi := A000720(n) ; pi*(n-pi) ; end proc: seq(A168048(n),n=1..120) ; # _R. J. Mathar_, Nov 18 2009

%Y Cf. A000720, A062298.

%K nonn

%O 1,3

%A _Daniel Tisdale_, Nov 17 2009

%E a(1) and terms after a(16) from _R. J. Mathar_, Nov 18 2009

%E Edited by _Jon E. Schoenfield_, May 10 2019