cp's OEIS Frontend

A227034 Composite numbers such that product_{i=1..k} (p_i/(p_i-1)) / sum_{i=1..k} (p_i/(p_i-1)) is an integer, where p_i are the k prime factors of n (with multiplicity).

%I A227034 #6 Jul 04 2013 14:33:02
%S A227034 4,16,72,132,256,800,1232,2208,2960,5184,5376,11904,19200,23760,39040,
%T A227034 41472,65536,72000,76032,76800,84816,203280,259200,288768,332928,
%U A227034 345600,373248,383040,416000,614400,628992,640000,663552,691200,1228800,1996800,2013312
%N A227034 Composite numbers such that product_{i=1..k} (p_i/(p_i-1)) / sum_{i=1..k} (p_i/(p_i-1)) is an integer, where p_i are the k prime factors of n (with multiplicity).
%C A227034 All terms are even numbers.
%H A227034 Paolo P. Lava, <a href="/A227034/b227034.txt">Table of n, a(n) for n = 1..100</a>
%e A227034 Prime factors of 1232 are 2^4, 7, 11 and ((2/(2-1))^4*7/(7-1)*11/(11-1)) / (4*2/(2-1)+7/(7-1)+11/(11-1)) = 2.
%p A227034 with(numtheory); ListA226365:=proc(q) local a, d, n, p;
%p A227034 for n from 2 to q do if not isprime(n) then p:=ifactors(n)[2];
%p A227034 a:=mul((op(1,d)/(op(1,d)-1))^op(2,d),d=p)/add((op(1,d)/(op(1,d)-1))*op(2,d),d=p);
%p A227034 if type(a,integer) then print(n); fi; fi;
%p A227034 od; end: ListA226365(10^10);
%Y A227034 Cf. A224346, A224912, A226365, A227248.
%K A227034 nonn
%O A227034 1,1
%A A227034 _Paolo P. Lava_, Jul 03 2013