A080213 - OEIS

%I #14 Nov 25 2023 07:08:17

%S 1,1,1,6,1,20,1,28,84,252,1,220,1,3432,3003,120,1,816,1,15504,116280,

%T 705432,1,2024,53130,10400600,2925,1184040,1,142506,1,496,193536720,

%U 2333606220,6724520,7140,1,35345263800,8122425444,658008,1,26978328,1

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

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

%H Robin Visser, <a href="/A080213/b080213.txt">Table of n, a(n) for n = 1..3000</a>

%F a(n) = binomial(n, A006530(n)). - _Michel Marcus_, May 06 2020

%t Table[Binomial[n,FactorInteger[n][[-1,1]]],{n,50}] (* _Harvey P. Dale_, Feb 25 2015 *)

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

%o (Sage)

%o def a(n):

%o     if n==1: return 1

%o     return binomial(n, factor(n)[-1][0])  # _Robin Visser_, Nov 25 2023

%Y Cf. A006530, A080211, A080212.

%K nonn

%O 1,4

%A _Reinhard Zumkeller_, Feb 06 2003