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 A374435 #12 Jul 13 2024 10:12:47
%S A374435 1,1,1,2,2,1,3,3,3,1,2,2,1,2,1,5,5,5,5,5,1,6,6,3,2,3,6,1,7,7,7,7,7,7,
%T A374435 7,1,2,2,1,2,1,2,1,2,1,3,3,3,1,3,3,1,3,3,1,10,10,5,10,5,2,5,10,5,10,1,
%U A374435 11,11,11,11,11,11,11,11,11,11,11,1
%N A374435 Triangle read by rows: T(n, k) = Product_{p in PF(n) difference PF(k)} p, where PF(a) is the set of the prime factors of a.
%e A374435 [ 0] 1;
%e A374435 [ 1] 1, 1;
%e A374435 [ 2] 2, 2, 1;
%e A374435 [ 3] 3, 3, 3, 1;
%e A374435 [ 4] 2, 2, 1, 2, 1;
%e A374435 [ 5] 5, 5, 5, 5, 5, 1;
%e A374435 [ 6] 6, 6, 3, 2, 3, 6, 1;
%e A374435 [ 7] 7, 7, 7, 7, 7, 7, 7, 1;
%e A374435 [ 8] 2, 2, 1, 2, 1, 2, 1, 2, 1;
%e A374435 [ 9] 3, 3, 3, 1, 3, 3, 1, 3, 3, 1;
%e A374435 [10] 10, 10, 5, 10, 5, 2, 5, 10, 5, 10, 1;
%e A374435 [11] 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 1;
%p A374435 PF := n -> ifelse(n = 0, {}, NumberTheory:-PrimeFactors(n)):
%p A374435 A374435 := (n, k) -> mul(PF(n) minus PF(k)):
%p A374435 seq(print(seq(A374435(n, k), k = 0..n)), n = 0..11);
%t A374435 nn = 12; Do[Set[s[i], FactorInteger[i][[All, 1]]], {i, 0, nn}]; s[0] = {1}; Table[Apply[Times, Complement[s[n], s[k]]], {n, 0, nn}, {k, 0, n}] // Flatten (* _Michael De Vlieger_, Jul 11 2024 *)
%o A374435 (Python) # Function A374435 defined in A374433.
%o A374435 for n in range(12): print([A374435(n, k) for k in range(n + 1)])
%Y A374435 Family: A374433 (intersection), A374434 (symmetric difference), this sequence (difference), A374436 (union).
%Y A374435 Cf. A007947 (column 0), A000034 (central terms).
%K A374435 nonn,tabl
%O A374435 0,4
%A A374435 _Peter Luschny_, Jul 10 2024