A077679 Squarefree numbers beginning with 3.

3, 30, 31, 33, 34, 35, 37, 38, 39, 301, 302, 303, 305, 307, 309, 310, 311, 313, 314, 317, 318, 319, 321, 322, 323, 326, 327, 329, 330, 331, 334, 335, 337, 339, 341, 345, 346, 347, 349, 353, 354, 355, 357, 358, 359, 362, 365, 366, 367, 370, 371, 373, 374, 377

Offset: 1

Author

Amarnath Murthy, Nov 16 2002

Keywords

• base
• easy
• nonn

Comments

Intersection of A005117 and A217395. - Michel Marcus, Sep 14 2013

Lower density is 1/(5*Pi^2), upper density is 5/(3*Pi^2). - Charles R Greathouse IV, Nov 05 2017

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A077677, A077678, A077680, A077681, A077682, A077683, A077684, A077685.

Programs

Mathematica

Select[Range[400],SquareFreeQ[#]&&IntegerDigits[#][[1]]==3&] (* Harvey P. Dale, Oct 10 2018 *)

PARI

isok(n) = (issquarefree(n) && (digits(n, 10)[1] == 3)) \\ Michel Marcus, Jul 31 2013

Extensions

More terms from Sascha Kurz, Jan 28 2003