cp's OEIS Frontend

A163173 The n-th product of three primes divided by its central prime factor.

%I A163173 #8 Jun 05 2023 18:53:07
%S A163173 4,6,6,10,9,14,10,14,22,15,10,26,21,22,34,14,15,38,26,46,14,33,34,21,
%T A163173 22,38,58,39,62,25,26,46,21,74,51,22,82,33,34,57,86,58,35,26,62,94,38,
%U A163173 39,69,106,74,46,33,118,34,22,122,35,82,51,86,87,38,134,39,55,93,94,142,57,26
%N A163173 The n-th product of three primes divided by its central prime factor.
%C A163173 All entries are in A001358.
%H A163173 Robert Israel, <a href="/A163173/b163173.txt">Table of n, a(n) for n = 1..10000</a>
%F A163173 a(n) = A014612(n)/A162361(n).
%e A163173 a(1)=2*2*2/2=4. a(2)=2*2*3/2=6. a(3)=2*3*3/3=6. a(4)=2*2*5/2=10. a(5)=3*3*3/3 = 9.
%p A163173 f:= proc(n) local P;
%p A163173    if numtheory:-bigomega(n) <> 3 then return NULL fi;
%p A163173    P:= numtheory:-factorset(n);
%p A163173    min(P)*max(P)
%p A163173 end proc:
%p A163173 map(f, [$1..500]); # _Robert Israel_, Jun 05 2023
%Y A163173 Cf. A014612, A162361.
%K A163173 nonn,look
%O A163173 1,1
%A A163173 _Juri-Stepan Gerasimov_, Jul 22 2009
%E A163173 a(57) corrected by _R. J. Mathar_, Jul 25 2009