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A080211 a(n) = binomial(n, smallest prime factor of n). 4

%I

%S 1,1,1,6,1,15,1,28,84,45,1,66,1,91,455,120,1,153,1,190,1330,231,1,276,

%T 53130,325,2925,378,1,435,1,496,5456,561,324632,630,1,703,9139,780,1,

%U 861,1,946,14190,1035,1,1128,85900584,1225,20825,1326,1,1431,3478761

%N a(n) = binomial(n, smallest prime factor of n).

%C For n>1: a(n)=1 iff n is prime.

%F a(n) = binomial(n, A020639(n)). - _Michel Marcus_, May 06 2020

%t Table[Binomial[n,FactorInteger[n][[1,1]]],{n,60}] (* _Harvey P. Dale_, Apr 12 2011 *)

%o (PARI) a(n) = if (n==1, 1, binomial(n, vecmin(factor(n)[,1]))); \\ _Michel Marcus_, May 06 2020

%Y Cf. A020639, A080212, A080213.

%K nonn

%O 1,4

%A _Reinhard Zumkeller_, Feb 06 2003

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Last modified May 25 19:19 EDT 2022. Contains 354071 sequences. (Running on oeis4.)