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A130829 2n+1 appears 2n times. 2
3, 3, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7, 9, 9, 9, 9, 9, 9, 9, 9, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..72.

FORMULA

a(n) = 2*floor(sqrt(n)+1/2)+1. - Mikael Aaltonen, Jan 14 2015

From Robert Israel, Jan 14 2015: (Start)

G.f.: x/(1-x)*(1+2*sum(m>=0, x^(m*(m+1))) = x/(1-x)*(1+x^(-1/4)*theta_2(0,x)) where theta_2 is the second Jacobi theta function.

a(2n) = a(2n-1) = 2*A002024(n)+1.

a(n) = A001670(n)+1.

(End)

MAPLE

seq(2*n+1 $ 2*n, n=1..10); # Robert Israel, Jan 14 2015

CROSSREFS

Cf. A001670, A002024, A003057.

Sequence in context: A265182 A251549 A129972 * A196386 A035158 A196172

Adjacent sequences:  A130826 A130827 A130828 * A130830 A130831 A130832

KEYWORD

nonn

AUTHOR

Paul Curtz, Jul 17 2007

STATUS

approved

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Last modified April 9 16:39 EDT 2020. Contains 333361 sequences. (Running on oeis4.)