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 A160401 #14 Mar 13 2018 04:40:26
%S A160401 4,4,4,6,4,6,4,6,6,4,10,4,6,4,10,6,10,12,12,10,6,14,6,15,4,15,6,14,8,
%T A160401 14,6,20,20,6,14,8,9,8,21,12,10,12,21,8,9,10,18,24,28,30,30,28,24,18,
%U A160401 10,22,10,9,8,35,6,35,8,9,10,22,12,22,30,36,40,42,42,40,36,30,22,12,26,12,33
%N A160401 Table read by antidiagonals: a(m,n) = the smallest composite multiple of both m and n.
%C A160401 a(p,1) = a(1,p) = a(p,p) = 2p, where p = any one prime. a(1,1) = 4. Otherwise, a(m,n) = lcm(m,n).
%e A160401 Array begins:
%e A160401 4, 4, 6, 4, 10, 6, ...
%e A160401 4, 4, 6, 4, 10, 6, ...
%e A160401 6, 6, 6, 12, 15, 6, ...
%e A160401 4, 4, 12, 4, 20, 12, ...
%e A160401 10, 10, 15, 20, 10, 30, ...
%e A160401 6, 6, 6, 12, 30, 6, ...
%e A160401 ...
%o A160401 (PARI) T(n, k) = {my(j = lcm(n, k), c = j); while (isprime(c) || (c==1), c += j); c;}
%o A160401 tabl(nn) = for (n=1, nn, for (k=1, nn, print1(T(n, k), ", ")); print); \\ _Michel Marcus_, Mar 13 2018
%Y A160401 Cf. A003990.
%K A160401 nonn,tabl
%O A160401 1,1
%A A160401 _Leroy Quet_, May 12 2009
%E A160401 Extended by _Ray Chandler_, Jun 18 2009