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 A305565 #6 Jun 05 2018 22:36:08
%S A305565 1,1,1,1,0,1,2,1,0,1,1,0,0,0,1,7,1,1,0,0,1,1,0,0,0,0,0,1,4,2,0,1,0,0,
%T A305565 0,1,2,0,1,0,0,0,0,0,1,7,1,0,0,1,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,1,32,7,
%U A305565 2,1,0,1,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0
%N A305565 Regular triangle where T(n,k) is the number of finite sets of positive integers with least common multiple n and greatest common divisor k.
%F A305565 If k divides n then T(n,k) = T(n/k,1) = A305564(n/k); otherwise T(n,k) = 0.
%e A305565 The T(12,2) = 7 sets are {2,12}, {4,6}, {2,4,6}, {2,4,12}, {2,6,12}, {4,6,12}, {2,4,6,12}.
%e A305565 Triangle begins:
%e A305565 1
%e A305565 1 1
%e A305565 1 0 1
%e A305565 2 1 0 1
%e A305565 1 0 0 0 1
%e A305565 7 1 1 0 0 1
%e A305565 1 0 0 0 0 0 1
%e A305565 4 2 0 1 0 0 0 1
%e A305565 2 0 1 0 0 0 0 0 1
%e A305565 7 1 0 0 1 0 0 0 0 1
%e A305565 1 0 0 0 0 0 0 0 0 0 1
%e A305565 32 7 2 1 0 1 0 0 0 0 0 1
%t A305565 Table[Length[Select[Subsets[Divisors[n]],And[GCD@@#==k,LCM@@#==n]&]],{n,20},{k,n}]
%Y A305565 Cf. A076078, A181819, A281116, A285572, A290103, A304818, A305563, A305564, A305566, A305567.
%K A305565 nonn,tabl
%O A305565 1,7
%A A305565 _Gus Wiseman_, Jun 05 2018