OFFSET
1,2
COMMENTS
When n is a square, a(n) is equal to 0, but the converse is not true, see A034096. - Michel Marcus, Sep 21 2015
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
sqrt(1) = 1.00000000... hence a(1) = 0.
sqrt(2) = 1.41421356... hence a(2) = 4.
sqrt(3) = 1.73205080... hence a(3) = 7.
sqrt(4) = 2.00000000... hence a(4) = 0.
Note that 26 = 2 * 13 and sqrt(26) = 5.09901951... so a(26) = 0 even though 26 is not a perfect square.
MAPLE
A023961 := proc(n) return floor(10*sqrt(n)) mod 10: end: seq(A023961(n), n=1..100); # Nathaniel Johnston, May 04 2011
MATHEMATICA
Array[Function[n, RealDigits[N[Power[n, 1/2], 10], 10] // (#[[1, #[[2]] + 1]]) &], 110]
fd[n_] := Module[{rd = RealDigits[Sqrt[n], 10, 10]}, First[rd][[Last[rd] + 1]]]; Array[fd, 90] (* Harvey P. Dale, Jan 16 2014 *)
PROG
(PARI) a(n) = floor(10*sqrt(n)) % 10; \\ Michel Marcus, Sep 21 2015
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
STATUS
approved