OFFSET
1,2
COMMENTS
Numbers n such that for each d | n, there is some 2-densely divisible (A174973) number d' such that d/2 < d' <= d.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
PROG
(PARI) dense(n, k)=my(d=divisors(n)); for(i=2, #d, if(d[i]>k*d[i-1], return(0))); 1
is(n)=my(d=select(k->dense(k, 2), divisors(n))); if(!#d||2*d[#d]<n, return(0)); for(i=2, #d, if(d[i]>2*d[i-1], return(0))); 1
CROSSREFS
KEYWORD
nonn
AUTHOR
Charles R Greathouse IV, Jul 23 2013
STATUS
approved