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A103128 n appears 2 * ceiling(n/2) times. 6
1, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = floor(sqrt(2n-1)).

From Robert Israel, Sep 12 2016: (Start)

a(n+1) = a(n)+1 for n in A007590, otherwise a(n+1) = a(n).

G.f.: x*Theta3(x^2)/(2*(1-x)) + sqrt(x)*Theta2(x^2)/(2*(1-x)) - x/(2*(1-x)), where Theta2 and Theta3 are Jacobi Theta functions. (End)

MAPLE

seq(floor(sqrt(2*n-1)), n=1..100); # Robert Israel, Sep 12 2016

MATHEMATICA

Table[Floor[Sqrt[2n-1]], {n, 1, 100}] (* Mohammad K. Azarian, Jun 15 2016 *)

PROG

(Haskell)

a103128 = a000196 . (subtract 1) . (* 2)

-- Reinhard Zumkeller, Feb 12 2012

CROSSREFS

Cf. A172471, A000196, A005408, A007590.

Sequence in context: A071626 A182008 A106457 * A156080 A271058 A107320

Adjacent sequences:  A103125 A103126 A103127 * A103129 A103130 A103131

KEYWORD

easy,nonn

AUTHOR

Giovanni Teofilatto, Mar 17 2005

EXTENSIONS

Edited by Franklin T. Adams-Watters, Apr 20 2010

STATUS

approved

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Last modified August 17 11:40 EDT 2017. Contains 290635 sequences.