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A176170 Smallest prime-factor of n-th product of 4 distinct primes. 4
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, 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, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A020639(A046386(n)). - Antti Karttunen, Dec 06 2017

MATHEMATICA

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

PROG

(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

CROSSREFS

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

Sequence in context: A105514 A214081 A194338 * A062153 A217693 A204560

Adjacent sequences:  A176167 A176168 A176169 * A176171 A176172 A176173

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Apr 10 2010

STATUS

approved

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Last modified November 14 04:53 EST 2019. Contains 329108 sequences. (Running on oeis4.)