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 A374433 #21 Jul 13 2024 10:12:36
%S A374433 1,1,1,1,1,2,1,1,1,3,1,1,2,1,2,1,1,1,1,1,5,1,1,2,3,2,1,6,1,1,1,1,1,1,
%T A374433 1,7,1,1,2,1,2,1,2,1,2,1,1,1,3,1,1,3,1,1,3,1,1,2,1,2,5,2,1,2,1,10,1,1,
%U A374433 1,1,1,1,1,1,1,1,1,11,1,1,2,3,2,1,6,1,2,3,2,1,6
%N A374433 Triangle read by rows: T(n, k) = Product_{p in PF(n) intersect PF(k)} p, where PF(a) is the set of the prime factors of a.
%H A374433 Michael De Vlieger, <a href="/A374433/a374433.png">Plot T(n,k) at (x,y) = (k,-n)</a>, n = 0..1024, showing 1 in gray, primes in red, and composites in green.
%F A374433 T(n, k) = 1 for k = 0, for k > 0: T(n, k) = rad(gcd(n, k)), where rad = A007947 and gcd = A050873. - _Michael De Vlieger_, Jul 11 2024
%e A374433 [ 0] 1;
%e A374433 [ 1] 1, 1;
%e A374433 [ 2] 1, 1, 2;
%e A374433 [ 3] 1, 1, 1, 3;
%e A374433 [ 4] 1, 1, 2, 1, 2;
%e A374433 [ 5] 1, 1, 1, 1, 1, 5;
%e A374433 [ 6] 1, 1, 2, 3, 2, 1, 6;
%e A374433 [ 7] 1, 1, 1, 1, 1, 1, 1, 7;
%e A374433 [ 8] 1, 1, 2, 1, 2, 1, 2, 1, 2;
%e A374433 [ 9] 1, 1, 1, 3, 1, 1, 3, 1, 1, 3;
%e A374433 [10] 1, 1, 2, 1, 2, 5, 2, 1, 2, 1, 10;
%e A374433 [11] 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11;
%p A374433 PF := n -> ifelse(n = 0, {}, NumberTheory:-PrimeFactors(n)):
%p A374433 A374433 := (n, k) -> mul(PF(n) intersect PF(k)):
%p A374433 seq(seq(A374433(n, k), k = 0..n), n = 0..12);
%t A374433 nn = 12; Do[Set[s[i], FactorInteger[i][[All, 1]]], {i, 0, nn}]; s[0] = {1};
%t A374433 Table[Times @@ Intersection[s[k], s[n]], {n, 0, nn}, {k, 0, n}] // Flatten (* _Michael De Vlieger_, Jul 11 2024 *)
%o A374433 (Python)
%o A374433 from math import prod
%o A374433 from sympy import primefactors
%o A374433 def PF(n): return set(primefactors(n)) if n > 0 else set({})
%o A374433 def PrimeIntersect(n, k): return prod(PF(n).intersection(PF(k)))
%o A374433 def PrimeSymDiff(n, k): return prod(PF(n).symmetric_difference(PF(k)))
%o A374433 def PrimeUnion(n, k): return prod(PF(n).union(PF(k)))
%o A374433 def PrimeDiff(n, k): return prod(PF(n).difference(PF(k)))
%o A374433 A374433 = PrimeIntersect; A374434 = PrimeSymDiff
%o A374433 A374435 = PrimeDiff; A374436 = PrimeUnion
%o A374433 for n in range(11): print([A374433(n, k) for k in range(n + 1)])
%Y A374433 Family: this sequence (intersection), A374434 (symmetric difference), A374435 (difference), A374436 (union).
%Y A374433 Cf. A007947 (main diagonal and central terms), A374432 (row sums), A374431 (row product).
%K A374433 nonn,tabl,easy
%O A374433 0,6
%A A374433 _Peter Luschny_, Jul 10 2024