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a(n) is root of square starting with digit 5: first term of runs.
2

%I #11 Oct 10 2019 03:59:38

%S 23,71,224,708,2237,7072,22361,70711,223607,707107,2236068,7071068,

%T 22360680,70710679,223606798,707106782,2236067978,7071067812,

%U 22360679775,70710678119,223606797750,707106781187,2236067977500

%N a(n) is root of square starting with digit 5: first term of runs.

%F a(n) = ceiling(sqrt(5*10^n)), n > 1.

%t Table[Ceiling @ Sqrt[5 * 10^n], {n, 2 , 24}] (* _Amiram Eldar_, Oct 08 2019 *)

%Y Cf. A067475 (squares), A035076 (2..9).

%K nonn,base

%O 2,1

%A _Patrick De Geest_, Nov 15 1998