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The n-th product of three primes divided by its central prime factor.
1

%I #8 Jun 05 2023 18:53:07

%S 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 22,38,58,39,62,25,26,46,21,74,51,22,82,33,34,57,86,58,35,26,62,94,38,

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

%C All entries are in A001358.

%H Robert Israel, <a href="/A163173/b163173.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A014612(n)/A162361(n).

%e 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 f:= proc(n) local P;

%p if numtheory:-bigomega(n) <> 3 then return NULL fi;

%p P:= numtheory:-factorset(n);

%p min(P)*max(P)

%p end proc:

%p map(f, [$1..500]); # _Robert Israel_, Jun 05 2023

%Y Cf. A014612, A162361.

%K nonn,look

%O 1,1

%A _Juri-Stepan Gerasimov_, Jul 22 2009

%E a(57) corrected by _R. J. Mathar_, Jul 25 2009