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A279420
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Numbers k such that k^2 has an odd number of digits and the middle digit is 0.
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24
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10, 20, 30, 100, 105, 138, 145, 155, 179, 195, 200, 205, 217, 226, 241, 243, 245, 247, 249, 251, 253, 255, 257, 259, 274, 283, 295, 300, 305, 1000, 1005, 1010, 1015, 1020, 1025, 1030, 1049, 1054, 1068, 1082, 1091, 1100, 1114, 1127, 1136, 1149, 1158, 1162, 1175
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OFFSET
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1,1
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LINKS
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EXAMPLE
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10^2 = 1(0)0, 195^2 = 38(0)25, 1000^2 = 100(0)000.
The sequences of squares starts: 100, 400, 900, 10000, 11025, 19044, 21025, 24025, 32041, 38025, 40000, ...
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MATHEMATICA
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Select[Range@ 1175, Function[w, And[OddQ@ Length@ w, First@ Take[w, {Ceiling[Length[w]/2]}] == 0]]@ IntegerDigits[#^2] &] (* Michael De Vlieger, Dec 12 2016 *)
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PROG
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(PARI) isok(n) = my(d=digits(n^2)); (#d % 2) && (d[#d\2 + 1] == 0); \\ Michel Marcus, Dec 18 2016
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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