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 A128060 #23 May 23 2025 10:15:58
%S A128060 -1,1,1,1,1,9,1,1,15,1,1,21,1,25,27,1,1,33,35,1,39,1,1,45,1,49,51,1,
%T A128060 55,57,1,1,63,65,1,69,1,1,75,77,1,81,1,85,87,1,91,93,95,1,99,1,1,105,
%U A128060 1,1,111,1,115,117,119,121,123,125,1,129,1,133,135,1,1,141,143,145,147
%N A128060 a(n) = 2*n - numerator((2*n-1)^2/(2*(2*n)!)).
%C A128060 Odd composite numbers with placeholders for primes between them.
%H A128060 Ivan V. Morozov, <a href="https://arxiv.org/abs/2505.16201">On Quotients of a More General Theorem of Wilson</a>, arXiv:2505.16201 [math.NT], 2025. See denominators of Z+ p. 9.
%F A128060 a(n) = 2*n - A128059(n).
%F A128060 a(n) = (A217983(n-1) * (2*n-1))/A160479(n) for n >= 3. - _Johannes W. Meijer_, Oct 25 2012
%F A128060 a(0) = -1, a(n) = gcd(2*n-1, (2*n-2)!), n > 0. - _Wesley Ivan Hurt_, Jan 05 2014
%p A128060 A128060 := proc(n): 2*n - numer((2*n-1)^2/(2*(2*n)!)) end: seq(A128060(n), n=0..62);
%p A128060 # End program 1 [_Johannes W. Meijer_, Oct 25 2012]
%p A128060 A128060 := proc(n) local n1: n1:=2*n-1: if type(n1, prime) then A128060(n) := 1 else A128060(n) := n1 fi: end: seq(A128060(n), n=0..62);
%p A128060 # End program 2 [_Johannes W. Meijer_, Oct 25 2012]
%t A128060 Table[2n - Numerator[(2n - 1)^2/(2(2n)!)], {n, 0, 74}] (* _Alonso del Arte_, Jan 05 2014 *)
%Y A128060 Cf. A128059, A160479, A217983.
%K A128060 easy,sign
%O A128060 0,6
%A A128060 _Paul Barry_, Feb 13 2007
%E A128060 More terms from _Michel Marcus_, May 23 2025