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 A374464 #12 Jul 12 2024 14:23:46
%S A374464 1,2,3,6,40,120,351,702,1000,3000,14040,351000
%N A374464 Numbers k such that the odd parts of k and sigma(A003961(k)) are equal, where A003961 is fully multiplicative function with a(prime(i)) = prime(i+1), and sigma is the sum of divisors function.
%C A374464 If x and y are included, and they are coprime (gcd(x,y) = 1), then x*y is also included.
%C A374464 A003961 applied to this sequence gives the odd terms of A374463, which after 1 is a subsequence of A347391.
%C A374464 Conjecture: the sequence is finite.
%F A374464 {k | A000265(k) = A000265(sigma(A003961(k)))}.
%e A374464 351 = 3^3 * 13 is included as sigma(A003961(351)) = sigma(2125) = 2808, with A000265(2808) = A000265(351) = 351.
%o A374464 (PARI)
%o A374464 A000265(n) = (n>>valuation(n,2));
%o A374464 A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
%o A374464 isA374464(n) = (A000265(sigma(A003961(n)))==A000265(n));
%Y A374464 Cf. A000203, A000265, A003961, A003973, A347391, A374463.
%Y A374464 After the initial 1, a subsequence of A348738. Cf. also A326042.
%K A374464 nonn,hard,more
%O A374464 1,2
%A A374464 _Antti Karttunen_, Jul 11 2024