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A241079
If n is a perfect square, a(n) = 0. If n is not a perfect square, a(n) is the number of final digits necessary to rule out n as a perfect square, or -1 if cannot be ruled out as a perfect square using any group of final digits.
0
0, 1, 1, 0, 2, 2, 1, 1, 0, 2, 2, 1, 1, 2, 2, 0, 1, 1, 2, 2, 3, 1, 1, 4, 0, 2, 1, 1, 3, 2, 2, 1, 1, 2, 2, 0, 1, 1, 2, 2, -1, 1, 1, 4, 2, 2, 1, 1, 0, 2, 2, 1, 1, 2, 2, 4, 1, 1, 2, 2, 3, 1, 1, 0, 2, 2, 1, 1, 3, 2, 2, 1, 1, 2, 2, 4, 1, 1, 2, 2, 0, 1, 1, 5, 2, 2, 1
OFFSET
1,5
COMMENTS
To define the n-digit ending of a number with fewer than n digits, insert 0's in front of it. For example, the 2-digit ending of 5 is 05.
EXAMPLE
a(24) cannot be 3 because 024 is a valid ending of a square (32^2 = 1024).
CROSSREFS
Cf. A241081 (numbers k such that a(k) = -1).
Sequence in context: A269317 A119557 A125919 * A061198 A195011 A290942
KEYWORD
sign,base
AUTHOR
J. Lowell, Apr 15 2014
EXTENSIONS
Terms corrected by and more terms from Jinyuan Wang, Aug 21 2021
STATUS
approved