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A077678 Squarefree numbers beginning with 2. 12
2, 21, 22, 23, 26, 29, 201, 202, 203, 205, 206, 209, 210, 211, 213, 214, 215, 217, 218, 219, 221, 222, 223, 226, 227, 229, 230, 231, 233, 235, 237, 238, 239, 241, 246, 247, 249, 251, 253, 254, 255, 257, 258, 259, 262, 263, 265, 266, 267, 269, 271, 273, 274 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Intersection of A005117 and A217394. - Michel Marcus, Sep 14 2013
Lower density is 3/(10*Pi^2), upper density is 20/(9*Pi^2). - Charles R Greathouse IV, Nov 05 2017
LINKS
MATHEMATICA
s2Q[n_]:=First[IntegerDigits[n]]==2 && 1==Max@@Last/@FactorInteger[n]; Select[Range[274], s2Q[#] &] (* Jayanta Basu, May 22 2013 *)
PROG
(PARI) is(n)=n>1 && digits(n)[1]==2 && issquarefree(n) \\ Charles R Greathouse IV, Nov 05 2017
CROSSREFS
Sequence in context: A371060 A171549 A355404 * A037309 A037315 A359385
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 16 2002
EXTENSIONS
More terms from Sascha Kurz, Jan 28 2003
STATUS
approved

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Last modified March 29 08:45 EDT 2024. Contains 371267 sequences. (Running on oeis4.)