OFFSET
1,1
COMMENTS
Lower density is 3/(20*Pi^2), upper density is 4/(3*Pi^2). - Charles R Greathouse IV, Nov 05 2017
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[499], First[IntegerDigits[#]]==4&&SquareFreeQ[#]&] (* Harvey P. Dale, Apr 24 2018 *)
PROG
(PARI) is(n)=n>40 && digits(n)[1]==4 && issquarefree(n) \\ Charles R Greathouse IV, Nov 05 2017
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 16 2002
EXTENSIONS
More terms from Sascha Kurz, Jan 28 2003
STATUS
approved