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 A346663 #16 Oct 17 2021 12:07:06
%S A346663 0,0,2,2,4,4,6,6,8,8,10,10,12,12,14,14,16,16,18,18,20,20,22,22,24,24,
%T A346663 26,26,28,28,30,30,32,32,34,34,36,36,38,38,40,40,42,42,44,44,46,46,48,
%U A346663 48,50,50,52,52,54,54,56,56,58,58,60,60,62,62,64,64,66,66,68,68,70,70,72,72
%N A346663 The number of nonreal roots of Sum_{k=0..n} prime(k+1)*x^k.
%C A346663 This agrees with A052928 until n = 2436. a(2436) = 2434 and A052928(2436) = 2436. For n >= 2436 we have a(n) = n-2 for n even and a(n) = n - 1 for n odd, for an as yet undetermined number of n. A052928(n) = n - (n mod 2) for all n. See the paper by W. Clark and M. Shattuck linked to below.
%H A346663 W. Edwin Clark and Mark Shattuck, <a href="https://arxiv.org/abs/2107.05572">The Integer Sequence Transform a --> b where b_n is the Number of Real Roots of the Polynomial a_0 + a_1 x + a_2 x^2 + ... + a_n x^n</a>, arXiv:2107.05572 [math.CO], 2021.
%H A346663 <a href="/index/Se#sequences_which_agree_for_a_long_time">Index entries for sequences which agree for a long time but are different</a>
%Y A346663 Cf. A052928, A346442, A346443, A346444, A346445.
%K A346663 nonn
%O A346663 0,3
%A A346663 _W. Edwin Clark_, Jul 27 2021