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A124600
Position of the first 0 in the decimal expansion of the square root of n, or -1 if 0 never appears.
1
1, -1, 14, 5, -1, 5, 17, 11, 16, -1, 10, 10, 6, 3, 36, 12, -1, 6, 7, 13, 37, 16, 4, 26, 52, -1, 2, 12, 6, 9, 11, 13, 16, 14, 4, 5, -1, 2, 8, 18, 10, 3, 4, 12, 10, 3, 20, 9, 6, -1, 2, 48, 6, 4, 49, 11, 32, 13, 9, 15, 19, 4, 5, 21, -1, 2, 5, 24, 17, 3, 6, 19, 16, 5, 3, 4, 11, 17, 7, 19, 9
OFFSET
0,3
COMMENTS
The real 0's representations after the decimal point of the expansion of the square root of perfect squares are ignored. In other words for sqrt(4) = 2.0000..., the trailing 0's are ignored.
LINKS
EXAMPLE
For n=14, the concatenated digits of sqrt(14) are The digit 0 in the 36th position of this string of digits so 36 is the 15th entry the table counting from the 0th entry.
MATHEMATICA
Join[{1}, Table[If[IntegerQ[Sqrt[n]], {{-1, -1}}, SequencePosition[ RealDigits[ Sqrt[n], 10, 100][[1]], {0}, 1]], {n, 100}][[All, 1]][[All, 1]]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 02 2016 *)
PROG
(PARI) a(n)={if(n==0, 1, forstep(m=0, oo, 10, my(z=select(x->x==0, digits(sqrtint(100^m*n)), 1)); if(#z, return(z[1])); if(!m&&issquare(n), return(-1)) ))} \\ Andrew Howroyd, Dec 18 2024
CROSSREFS
Sequence in context: A040188 A322776 A040186 * A340715 A344046 A084676
KEYWORD
base,easy,sign
AUTHOR
Cino Hilliard, Dec 22 2006, corrected Jul 18 2007
STATUS
approved