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 A345266 #37 Feb 05 2024 14:24:56
%S A345266 0,1,1,2,1,2,1,2,3,2,1,3,1,2,2,2,1,4,1,3,2,2,1,3,5,2,3,3,1,3,1,2,2,2,
%T A345266 2,5,1,2,2,3,1,3,1,3,4,2,1,3,7,6,2,3,1,4,2,3,2,2,1,4,1,2,4,2,2,3,1,3,
%U A345266 2,3,1,5,1,2,6,3,2,3,1,3,3,2,1,4,2,2,2,3,1,5,2,3,2,2,2,3,1,8,4,7,1,3,1,3,3
%N A345266 a(n) = Sum_{p|n, p prime} gcd(p,n/p).
%H A345266 Antti Karttunen, <a href="/A345266/b345266.txt">Table of n, a(n) for n = 1..65537</a>
%H A345266 <a href="/index/Ga#gcd">Index entries for sequences related to gcd's</a>.
%F A345266 a(p) = 1 for p prime.
%F A345266 From _Wesley Ivan Hurt_, Nov 21 2021: (Start)
%F A345266 a(n) = A056169(n) + A063958(n).
%F A345266 If n is squarefree, then a(n) = omega(n).
%F A345266 a(p^k) = p for primes p and k >= 2. (End)
%e A345266 a(18) = Sum_{p|18} gcd(p,18/p) = gcd(2,9) + gcd(3,6) = 1 + 3 = 4.
%t A345266 Table[Sum[GCD[k, n/k] (PrimePi[k] - PrimePi[k - 1]) (1 - Ceiling[n/k] + Floor[n/k]), {k, n}], {n, 100}]
%o A345266 (PARI) a(n) = my(f=factor(n), p); sum(k=1, #f~, p=f[k, 1]; gcd(p,n/p)); \\ _Michel Marcus_, Jun 16 2021
%o A345266 (PARI) A345266(n) = vecsum(apply(p->gcd(p,n/p), factor(n)[,1])); \\ _Antti Karttunen_, Nov 13 2021
%Y A345266 Cf. A001221 (omega), A007947 (rad), A008472 (sopf), A345302.
%Y A345266 Cf. A055155, A056169, A063958.
%K A345266 nonn,look
%O A345266 1,4
%A A345266 _Wesley Ivan Hurt_, Jun 13 2021
%E A345266 Data section extended up to 105 terms by _Antti Karttunen_, Nov 13 2021