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 A215284 #22 Nov 07 2024 08:32:35
%S A215284 5,8,12,18,20,21,24,28,32,40,44,48,52,53,56,60,68,69,72,76,77,80,84,
%T A215284 88,92,96,99,104,108,112,116,120,124,125,126,128,132,136,140,141,148,
%U A215284 150,152,156,160,162,164,165,168,172,176,180,184,188,189,192,197
%N A215284 Numbers m such that Sum_{k=1..m} (m - k | k) = 0, where (i|j) is the Kronecker symbol.
%C A215284 Appears to include all multiples of 4 that are not squares. - _Robert Israel_, Mar 11 2018
%H A215284 Amiram Eldar, <a href="/A215284/b215284.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..2830 from Robert Israel)
%p A215284 f:= n -> add(numtheory:-jacobi(n-k,k),k=1..n):
%p A215284 select(n -> f(n)=0, [$1..300]); # _Robert Israel_, Mar 11 2018
%t A215284 Select[ Range[200], Sum[ KroneckerSymbol[# - k, k], {k, 1, #}] == 0 & ] (* _Jean-François Alcover_, Jul 29 2013 *)
%o A215284 (Sage)
%o A215284 def A215200_row(n): return [kronecker_symbol(n-k, k) for k in (1..n)]
%o A215284 [n for n in (1..197) if sum(A215200_row(n)) == 0]
%o A215284 (PARI) is(m) = sum(k = 1, m, kronecker(m-k, k)) == 0; \\ _Amiram Eldar_, Nov 07 2024
%Y A215284 Cf. A215200, A215283, A215285.
%K A215284 nonn
%O A215284 1,1
%A A215284 _Peter Luschny_, Aug 07 2012