login
A077677
Squarefree numbers beginning with 1.
11
1, 10, 11, 13, 14, 15, 17, 19, 101, 102, 103, 105, 106, 107, 109, 110, 111, 113, 114, 115, 118, 119, 122, 123, 127, 129, 130, 131, 133, 134, 137, 138, 139, 141, 142, 143, 145, 146, 149, 151, 154, 155, 157, 158, 159, 161, 163, 165, 166, 167, 170, 173, 174, 177
OFFSET
1,2
COMMENTS
Intersection of A005117 and A131835. - Michel Marcus, Sep 14 2013
Lower density is 3/(5*Pi^2), upper density is 10/(3*Pi^2). - Charles R Greathouse IV, Nov 05 2017
LINKS
MATHEMATICA
Select[Range[177], First[IntegerDigits[#]]==1 && SquareFreeQ[#] &] (* Jayanta Basu, May 23 2013 *)
PROG
(PARI) is(n)=n>0 && digits(n)[1]==1 && issquarefree(n) \\ Charles R Greathouse IV, Nov 05 2017
(PARI) list(lim)=my(v=List([1])); for(d=1, #Str(lim\=1)-1, my(D=10^d); forsquarefree(n=D, min(2*D, lim), listput(v, n[1]))); Vec(v) \\ Charles R Greathouse IV, Jan 10 2023
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 16 2002
EXTENSIONS
Corrected and extended by Sascha Kurz, Jan 28 2003
STATUS
approved