login
Numbers whose square has initial digit '6'.
4

%I #19 Aug 25 2021 03:44:34

%S 8,25,26,78,79,80,81,82,83,245,246,247,248,249,250,251,252,253,254,

%T 255,256,257,258,259,260,261,262,263,264,775,776,777,778,779,780,781,

%U 782,783,784,785,786,787,788,789,790,791,792,793,794,795,796,797,798,799

%N Numbers whose square has initial digit '6'.

%H Harvey P. Dale, <a href="/A045860/b045860.txt">Table of n, a(n) for n = 1..1000</a>

%t Flatten[Table[Range[Ceiling[Sqrt[6*10^n]],Floor[Sqrt[7*10^n]]],{n,5}]] (* _Harvey P. Dale_, Apr 03 2013 *)

%o (Python)

%o from math import isqrt

%o def aupto(limit):

%o alst, d, end = [], 1, 0

%o while end < limit:

%o start, end = isqrt(6*10**d) + 1, isqrt(7*10**d-1)

%o alst.extend([an for an in list(range(start, end+1)) if an <= limit])

%o d += 1

%o return alst

%o print(aupto(799)) # _Michael S. Branicky_, Aug 25 2021

%Y Supersequence of A035073.

%Y Cf. A045789.

%K nonn,base

%O 1,1

%A _Jeff Burch_