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A045860 Numbers whose square has initial digit '6'.

%I A045860 #19 Aug 25 2021 03:44:34
%S A045860 8,25,26,78,79,80,81,82,83,245,246,247,248,249,250,251,252,253,254,
%T A045860 255,256,257,258,259,260,261,262,263,264,775,776,777,778,779,780,781,
%U A045860 782,783,784,785,786,787,788,789,790,791,792,793,794,795,796,797,798,799
%N A045860 Numbers whose square has initial digit '6'.
%H A045860 Harvey P. Dale, <a href="/A045860/b045860.txt">Table of n, a(n) for n = 1..1000</a>
%t A045860 Flatten[Table[Range[Ceiling[Sqrt[6*10^n]],Floor[Sqrt[7*10^n]]],{n,5}]] (* _Harvey P. Dale_, Apr 03 2013 *)
%o A045860 (Python)
%o A045860 from math import isqrt
%o A045860 def aupto(limit):
%o A045860     alst, d, end = [], 1, 0
%o A045860     while end < limit:
%o A045860         start, end = isqrt(6*10**d) + 1, isqrt(7*10**d-1)
%o A045860         alst.extend([an for an in list(range(start, end+1)) if an <= limit])
%o A045860         d += 1
%o A045860     return alst
%o A045860 print(aupto(799)) # _Michael S. Branicky_, Aug 25 2021
%Y A045860 Supersequence of A035073.
%Y A045860 Cf. A045789.
%K A045860 nonn,base
%O A045860 1,1
%A A045860 _Jeff Burch_