1,1

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

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)

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

Cf. A001670, A002024, A003057.

Sequence in context: A265182 A251549 A129972 * A196386 A035158 A196172

Adjacent sequences: A130826 A130827 A130828 * A130830 A130831 A130832

nonn

Paul Curtz, Jul 17 2007

approved