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 A354452 #22 Jan 17 2025 09:43:01
%S A354452 1,1,2,1,0,2,0,1,1,2,0,2,0,2,2,1,0,1,0,2,2,0,0,2,1,0,2,2,0,2,0,1,2,0,
%T A354452 2,3,0,0,0,2,0,2,0,2,2,0,0,2,1,1,0,2,0,2,2,2,0,0,0,4,0,0,2,1,2,2,0,0,
%U A354452 0,2,0,3,0,0,2,0,2,2,0,2,1,0,0,2,2,0,0,2,0,4,2,0,0,0,2,2,0,1,2,1,0,2,0,2,2
%N A354452 Number of middle divisors of 2*n.
%C A354452 a(n) is the number of middle divisors of the n-th even number.
%C A354452 a(n) is also the width of the terrace at the level 2*n starting from the top in the main diagonal of the stepped pyramid described in A245092.
%C A354452 a(n) is also the number of central subparts in the symmetric representation of sigma(2n). For more information about the subparts see A279387.
%H A354452 Antti Karttunen, <a href="/A354452/b354452.txt">Table of n, a(n) for n = 1..32768</a>
%F A354452 a(n) = A067742(2n).
%F A354452 a(n) = A067742(A005843(n)).
%t A354452 a[n_] := DivisorSum[2*n, 1 &, n <= #^2 < 4*n &]; Array[a, 100] (* _Amiram Eldar_, Jun 01 2022 *)
%o A354452 (PARI) A354452(n) = { n <<= 1; sumdiv(n, d, my(d2 = d^2); (n / 2 < d2 && d2 <= n << 1)); }; \\ _Antti Karttunen_, Jan 17 2025, after program in A067742 by _M. F. Hasler_, May 12 2008
%Y A354452 Bisection of A067742.
%Y A354452 Cf. A005843, A099777, A237048, A237270, A237271, A237593, A245092, A249351, A279387, A319796, A354451.
%K A354452 nonn
%O A354452 1,3
%A A354452 _Omar E. Pol_, May 30 2022