OFFSET
1,2
COMMENTS
Numbers k such that A008683(A132739(k)) is not zero, where A008683 is the Moebius mu function. - Antti Karttunen, Jun 21 2014
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ kn with k = 10*Pi^2/63. - Charles R Greathouse IV, Apr 16 2015
MAPLE
N:= 1000: # to get all terms <= N
sf:= select(numtheory:-issqrfree, {$1..N}):
map(t -> seq(t*5^i, i=0..floor(log[5](N/t))), sf);
# if using Maple 11 or earlier, uncomment the next line
# sort(convert(%, list)); # Robert Israel, Apr 16 2015
MATHEMATICA
lim = 102; sf = Select[Range[lim], SquareFreeQ]; lim5 = 5^Range[0, Log[5, lim]]; Select[Union[Flatten[Outer[Times, sf, lim5]]], # <= lim &]
PROG
(PARI) is(n)=issquarefree(n/5^valuation(n, 5)) \\ Charles R Greathouse IV, Jul 31 2011
(Scheme, with Antti Karttunen's IntSeq-library)
;; Reflecting essentially the above Pari-program, Antti Karttunen, Jun 21 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Jul 21 2011
STATUS
approved