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 A056691 #20 May 23 2025 15:40:19
%S A056691 1,1,2,2,2,1,2,3,3,2,2,3,2,2,3,4,2,2,2,3,4,2,2,4,3,2,4,4,2,3,2,5,3,2,
%T A056691 4,5,2,2,4,5,2,1,2,4,4,2,2,6,3,3,3,4,2,3,4,6,4,2,2,5,2,2,6,6,4,3,2,4,
%U A056691 3,3,2,7,2,2,5,4,4,2,2,7,5,2,2,5,4,2,3,6,2,5,3,4,4,2,3,7,2,3,5,5,2,3,2,6,6
%N A056691 Number of divisors d of n with gcd(d+1, n) = 1.
%H A056691 Amiram Eldar, <a href="/A056691/b056691.txt">Table of n, a(n) for n = 1..10000</a>
%e A056691 The positive divisors of 8 are 1, 2, 4 and 8. (2+1), (4+1) and (8+1) are relatively prime to 8, so a(8) = 3.
%t A056691 Table[Length[Select[Divisors[n],CoprimeQ[#+1,n]&]],{n,120}] (* _Harvey P. Dale_, Sep 07 2020 *)
%o A056691 (PARI) a(n) = sumdiv(n, d, gcd(d+1, n) == 1); \\ _Amiram Eldar_, May 23 2025
%Y A056691 Cf. A056692.
%K A056691 nonn
%O A056691 1,3
%A A056691 _Leroy Quet_, Aug 10 2000