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A257832
Squarefree numbers that are k*A005117(k) for some k.
1
1, 30, 42, 70, 165, 247, 330, 442, 570, 805, 1247, 1457, 1749, 1870, 1995, 2183, 2318, 2418, 2706, 2814, 2967, 3358, 3478, 4182, 4505, 4785, 5187, 5394, 5546, 5917, 6262, 7169, 7590, 7770, 8023, 8395, 9471, 9906, 10191, 10906, 11122, 11730, 11954, 12727, 13286, 14043, 15326, 16665, 17201
OFFSET
1,2
COMMENTS
k*A005117(k) is in the sequence iff k is squarefree and gcd(k,A005117(k)) = 1. - Robert Israel, May 22 2015
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
A005117(m) equal to k*A005117(k).
EXAMPLE
30 is in this sequence because the 5th squarefree is 6 and 5*6 = 30.
MAPLE
k:= 0:
count:= 0:
for m from 1 while count < 100 do
if numtheory:-issqrfree(m) then
k:= k+1;
if numtheory:-issqrfree(k) and igcd(k, m)=1 then
count:= count+1;
A[count]:= k*m;
fi
fi
od:
seq(A[i], i=1..count); # Robert Israel, May 22 2015
PROG
(PARI) list(lim)=my(v=List(), k, t); for(s=1, lim, if(issquarefree(s), t=k++*s; if(t>lim, return(Vec(v))); if(issquarefree(t), listput(v, t)))) \\ Charles R Greathouse IV, May 22 2015
CROSSREFS
Cf. A005117.
Sequence in context: A219742 A348557 A376800 * A050776 A268697 A258358
KEYWORD
nonn
AUTHOR
EXTENSIONS
Name corrected by Robert Israel, May 22 2015
STATUS
approved