A077685 - OEIS

A077685

Squarefree numbers beginning with 9.

91, 93, 94, 95, 97, 901, 902, 903, 905, 906, 907, 910, 911, 913, 914, 915, 917, 919, 921, 922, 923, 926, 929, 930, 933, 934, 935, 937, 938, 939, 941, 942, 943, 946, 947, 949, 951, 953, 955, 957, 958, 959, 962, 965, 966, 967, 969, 970, 971, 973, 974, 977, 978

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OFFSET

1,1

COMMENTS

Intersection of A005117 and A217402. - Michel Marcus, Sep 14 2013

Lower density is 1/(15*Pi^2), upper density is 2/(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[1000], SquareFreeQ[#]&&First[IntegerDigits[#]]==9&] (* Harvey P. Dale, Dec 15 2013 *)

PROG

(PARI) isok(n) = issquarefree(n) && (digits(n)[1] == 9); \\ Michel Marcus, Sep 14 2013