This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A130829 #22 Sep 21 2024 22:56:21
%S A130829 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,
%T A130829 11,13,13,13,13,13,13,13,13,13,13,13,13,15,15,15,15,15,15,15,15,15,15,
%U A130829 15,15,15,15,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17
%N A130829 2n+1 appears 2n times.
%F A130829 a(n) = 2*floor(sqrt(n)+1/2)+1. - _Mikael Aaltonen_, Jan 14 2015
%F A130829 From _Robert Israel_, Jan 14 2015: (Start)
%F A130829 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.
%F A130829 a(2n) = a(2n-1) = 2*A002024(n)+1.
%F A130829 a(n) = A001670(n)+1.
%F A130829 (End)
%p A130829 seq(2*n+1 $ 2*n, n=1..10); # _Robert Israel_, Jan 14 2015
%o A130829 (Python)
%o A130829 from math import isqrt
%o A130829 def A130829(n): return 1|((m:=isqrt(n))+int((n-m*(m+1)<<2)>=1)<<1) # _Chai Wah Wu_, Oct 17 2022
%Y A130829 Cf. A001670, A002024, A003057.
%K A130829 nonn,easy
%O A130829 1,1
%A A130829 _Paul Curtz_, Jul 17 2007