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a(n)=pi(n)*[pi(n)-pi(n-3)] where pi(n)=A000720(n).
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%I #2 Oct 15 2013 22:32:21

%S 0,1,4,4,6,3,8,4,4,0,5,5,12,6,6,0,7,7,16,8,8,0,9,9,9,0,0,0,10,10,22,

%T 11,11,0,0,0,12,12,12,0,13,13,28,14,14,0,15,15,15,0,0,0,16,16,16,0,0,

%U 0,17,17,36,18,18,0,0,0,19,19,19,0,20,20,42,21,21,0,0,0,22,22,22,0,23,23,23

%N a(n)=pi(n)*[pi(n)-pi(n-3)] where pi(n)=A000720(n).

%Y Cf. A049084, A000720, A010051, A000027, A090112.

%K nonn

%O 1,3

%A _Labos Elemer_, Jan 08 2004