A165664 - OEIS

%I #12 Dec 12 2023 07:48:09

%S 2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,

%T 8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,

%U 7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8,2,0,0,2,8,7,8

%N First digit of the decimal expansion of (n^2-2)/7 after the decimal point.

%C Periodic with period length 7.

%F a(n) = floor(10*(n^2-2)/7) mod 10. [R. J. Mathar, Sep 23 2009]

%e For n=2, (2^2-2)/7=0.285... and the digit after the point is 2.

%e For n=3, (3^2-2)/7=1.0000.., integer, and the digit is 0.

%e For n=4, (4^2-2)/7=2.0000, integer and the digit is 0.

%e For n=5, (5^2-2)/7=3.2857.. and the first decimal after the point is 2.

%t Table[IntegerPart[10*FractionalPart[N[(n^2-2)/7]]],{n,2,110}] (* _Harvey P. Dale_, Apr 08 2013 *)

%K nonn,base,less

%O 2,1

%A _Vincenzo Librandi_, Sep 24 2009