cp's OEIS Frontend

A100951 Number of ways to write n = p*q + r with three distinct primes p, q and r.

%I A100951 #6 Mar 30 2012 18:50:48
%S A100951 0,0,0,0,0,0,0,0,0,0,1,0,2,0,0,0,4,0,2,0,1,1,3,0,3,2,3,1,4,0,2,2,3,2,
%T A100951 3,0,5,4,3,2,5,0,4,3,5,4,3,1,4,3,5,4,6,1,3,4,6,6,4,0,3,7,6,5,6,1,6,6,
%U A100951 6,4,4,3,4,7,7,6,6,2,6,7,8,8,3,2,7,6,7,8,8,1,4,7,10,10,6,6,7,10,9,8,5,5,5,8
%N A100951 Number of ways to write n = p*q + r with three distinct primes p, q and r.
%C A100951 a(n)<=A100950(n)<=A100949(n)<=Min{A000720(n), A072000(n)}.
%C A100951 a(n) = A000040(i) + A006881(j) for some i and j, such that A000040(i) is not a factor of A006881(j);
%C A100951 a(A100952(n)) = 0.
%C A100951 a(A160373(n)) = n and a(m) <> n for m < A160373(n). [From _Reinhard Zumkeller_, May 11 2009]
%H A100951 R. Zumkeller, <a href="/A100951/b100951.txt">Table of n, a(n) for n = 1..10000</a>
%e A100951 A100949(21) = #{7+2*7, 11+2*5, 17+2*2} = 3,
%e A100951 a(21) = #{11+2*5} = 1.
%K A100951 nonn
%O A100951 1,13
%A A100951 _Reinhard Zumkeller_, Nov 23 2004