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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).
5
4, 16, 72, 132, 256, 800, 1232, 2208, 2960, 5184, 5376, 11904, 19200, 23760, 39040, 41472, 65536, 72000, 76032, 76800, 84816, 203280, 259200, 288768, 332928, 345600, 373248, 383040, 416000, 614400, 628992, 640000, 663552, 691200, 1228800, 1996800, 2013312
OFFSET
1,1
COMMENTS
All terms are even numbers.
LINKS
EXAMPLE
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.
MAPLE
with(numtheory); ListA226365:=proc(q) local a, d, n, p;
for n from 2 to q do if not isprime(n) then p:=ifactors(n)[2];
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);
if type(a, integer) then print(n); fi; fi;
od; end: ListA226365(10^10);
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Jul 03 2013
STATUS
approved