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 A023961 First digit after decimal point of square root of n. 13
 0, 4, 7, 0, 2, 4, 6, 8, 0, 1, 3, 4, 6, 7, 8, 0, 1, 2, 3, 4, 5, 6, 7, 8, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 1, 2, 3, 4, 4, 5, 6, 7, 7, 8, 9, 0, 0, 1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 0, 0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 8, 8, 9, 0, 0, 1, 1, 2, 2, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS When n is a square, a(n) is equal to 0, but the reciprocal is not true, see A034096. - Michel Marcus, Sep 21 2015 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A010879(A000196(100*n)). - Robert Israel, Jul 30 2015 EXAMPLE sqrt(1) = 1.00... hence a(1) = 0. sqrt(2) = 1.41... hence a(2) = 4. sqrt(3) = 1.73... hence a(3) = 7. 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 Cf. A111862, A111850, A111851, A111852, A111853, A111854, A111855, A111856, A111857, A111858, A111859. Sequence in context: A133982 A069179 A058377 * A147863 A019976 A021072 Adjacent sequences:  A023958 A023959 A023960 * A023962 A023963 A023964 KEYWORD nonn,easy,base AUTHOR STATUS approved

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