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A176170 Smallest prime-factor of n-th product of 4 distinct primes. 4


%S 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,2,3,2,2,2,2,2,2,

%T 2,2,2,3,2,2,2,2,2,2,2,3,2,2,2,2,2,2,3,2,2,2,2,2,2,2,3,2,2,2,2,2,2,2,

%U 2,2,2,2,2,3,2,2,2,2,2,2,2,2,2,3,2,2,3,2,2,2,2,3,2,2,2,2,2,3,2,2,2,3,2,2,2

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

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

%H Antti Karttunen, <a href="/A176170/b176170.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A020639(A046386(n)). - _Antti Karttunen_, Dec 06 2017

%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,f1[n]]],{n,0,2*7!}];lst

%o (PARI) n=0; i=0; while(i<10000,n++;if((4 == bigomega(n))&&(4 == omega(n)),i++;write("b176170.txt", i, " ", factor(n)[1,1]))); \\ _Antti Karttunen_, Dec 06 2017

%Y Cf. A020639, A046386, A006881, A007304, A070647, A096916, A096917, A096918, A096919

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Apr 10 2010

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Last modified December 9 00:32 EST 2019. Contains 329871 sequences. (Running on oeis4.)