A176171 - OEIS

%I #2 Mar 31 2012 12:38:35

%S 3,3,3,3,3,3,3,3,3,5,3,3,3,5,3,3,3,3,5,5,3,3,3,3,3,3,5,5,3,5,3,3,3,3,

%T 5,3,3,5,3,3,3,5,3,3,3,5,7,3,5,3,5,3,5,5,3,5,3,3,3,3,5,3,3,5,3,3,5,3,

%U 5,7,3,3,3,5,3,3,5,3,3,7,3,3,5,7,5,3,5,3,3,7,3,5,3,5,3,3,5,5,3,5,3,5,3,3,3

%N Second prime-factor of n-th product of 4 distinct primes.

%C FactorInteger[210]=2*3*5*7,...

%t f0[n_]:=Last/@FactorInteger[n]=={1,1,1,1};f1[n_]:=Min[First/@FactorInteger[n]];f2[n_]:=First/@FactorInteger[n][[2,1]];f3[n_]:=First/@FactorInteger[n][[3,1]];f4[n_]:=Max[First/@FactorInteger[n]];lst={};Do[If[f0[n],AppendTo[lst,f2[n]]],{n,0,2*7!}];lst

%Y Cf. A006881, A007304, A070647, A096916, A096917, A096918, A096919, A176170

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Apr 10 2010