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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

N. J. A. Sloane, Olivier Gérard

STATUS

approved

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Last modified December 3 14:15 EST 2016. Contains 278745 sequences.