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 A132391 Numbers whose square starts with 4 identical digits. 2
 2357, 2582, 3334, 4714, 5774, 6667, 8165, 8819, 9428, 10541, 10542, 10543, 10544, 10545, 14907, 14908, 14909, 18257, 18258, 18259, 21081, 21082, 21083, 23570, 23571, 25819, 25820, 27888, 27889, 29813, 29814, 31622, 33332, 33333 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE Example: 2357^2 = 5555449. MATHEMATICA Select[Range[10, 50000], Length[Union[Take[IntegerDigits[ #^2], 4]]] == 1 & ] Comment from Hans Havermann, Aug 30 2007: Here's a more generic Mathematica program that calculates the first q terms of squares starting with n identical digits: n=4; q=30; t=Table[(10^n-1)*i/9, {i, 1, 9}]; u=Sqrt[Union[t, 10*t]]; v=Sqrt[Union[t+1, 10*(t+1)]]; k=1; While[s=Sort[Flatten[Table[Union [Table[Range[Ceiling[10^j*u[[i]]], f=10^j*v[[i]]; If[IntegerQ[f], f=f-1]; Floor[f]], {i, 1, 18}]], {j, 0, k}]]]; Length[s]

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Last modified January 17 23:37 EST 2020. Contains 330995 sequences. (Running on oeis4.)