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 A374434 #20 Jul 13 2024 10:12:41
%S A374434 1,1,1,2,2,1,3,3,6,1,2,2,1,6,1,5,5,10,15,10,1,6,6,3,2,3,30,1,7,7,14,
%T A374434 21,14,35,42,1,2,2,1,6,1,10,3,14,1,3,3,6,1,6,15,2,21,6,1,10,10,5,30,5,
%U A374434 2,15,70,5,30,1,11,11,22,33,22,55,66,77,22,33,110,1
%N A374434 Triangle read by rows: T(n, k) = Product_{p in PF(n) symmetric difference PF(k)} p, where PF(a) is the set of the prime factors of a.
%F A374434 From _Michael De Vlieger_, Jul 11 2024: (Start)
%F A374434 T(0,0) = T(n,0) = rad(n)/rad(0) = 1 where rad = A007947;
%F A374434 T(n,k) = rad(k*n)/rad(gcd(k,n))
%F A374434 = A007947(k*n)/A007947(S(n,k)) where S = A050873
%F A374434 = A374436(n,k)/A374433(n,k). (End)
%e A374434 [ 0] 1;
%e A374434 [ 1] 1, 1;
%e A374434 [ 2] 2, 2, 1;
%e A374434 [ 3] 3, 3, 6, 1;
%e A374434 [ 4] 2, 2, 1, 6, 1;
%e A374434 [ 5] 5, 5, 10, 15, 10, 1;
%e A374434 [ 6] 6, 6, 3, 2, 3, 30, 1;
%e A374434 [ 7] 7, 7, 14, 21, 14, 35, 42, 1;
%e A374434 [ 8] 2, 2, 1, 6, 1, 10, 3, 14, 1;
%e A374434 [ 9] 3, 3, 6, 1, 6, 15, 2, 21, 6, 1;
%e A374434 [10] 10, 10, 5, 30, 5, 2, 15, 70, 5, 30, 1;
%e A374434 [11] 11, 11, 22, 33, 22, 55, 66, 77, 22, 33, 110, 1;
%p A374434 PF := n -> ifelse(n = 0, {}, NumberTheory:-PrimeFactors(n)):
%p A374434 A374434 := (n, k) -> mul(symmdiff(PF(n), PF(k))):
%p A374434 seq(print(seq(A374434(n, k), k = 0..n)), n = 0..11);
%t A374434 nn = 12; Do[Set[s[i], FactorInteger[i][[All, 1]]], {i, 0, nn}]; s[0] = {1}; Table[Times @@ SymmetricDifference[s[k], s[n]], {n, 0, nn}, {k, 0, n}] // Flatten (* _Michael De Vlieger_, Jul 11 2024 *)
%o A374434 (Python) # Function A374434 defined in A374433.
%o A374434 for n in range(11): print([A374434(n, k) for k in range(n + 1)])
%Y A374434 Family: A374433 (intersection), this sequence (symmetric difference), A374435 (difference), A374436 (union).
%Y A374434 Cf. A007947 (column 0), A000034 (central terms), A050873 (gcd).
%K A374434 nonn,tabl
%O A374434 0,4
%A A374434 _Peter Luschny_, Jul 10 2024