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 A287920 #22 Jul 04 2017 09:27:22 %S A287920 1,1,1,2,1,1,3,2,1,1,5,3,2,1,1,6,4,2,1,1,1,8,5,3,2,1,1,1,9,6,3,2,1,1, %T A287920 1,1,11,7,4,3,2,1,1,1,1,14,9,5,4,2,2,1,1,1,1,15,10,6,4,2,2,1,1,1,1,1, %U A287920 18,12,7,5,3,2,2,1,1,1,1,1,20,13,8,5,3,3,2,2,1,1,1,1,1 %N A287920 Triangle T(n,k) read by rows: T(n,k) = floor(prime(n)/prime(k)), n >= k >= 1. %C A287920 Alternate name: triangle of quotients of prime(n)/prime(k), n >= k >= 1. %e A287920 Triangle starts: %e A287920 n/k 1 2 3 4 5 6 7 8 9 10 11 12 %e A287920 1 1 %e A287920 2 1 1 %e A287920 3 2 1 1 %e A287920 4 3 2 1 1 %e A287920 5 5 3 2 1 1 %e A287920 6 6 4 2 1 1 1 %e A287920 7 8 5 3 2 1 1 1 %e A287920 8 9 6 3 2 1 1 1 1 %e A287920 9 11 7 4 3 2 1 1 1 1 %e A287920 10 14 9 5 4 2 2 1 1 1 1 %e A287920 11 15 10 6 4 2 2 1 1 1 1 1 %e A287920 12 18 12 7 5 3 2 2 1 1 1 1 1 %e A287920 T(11,3) = 6 because prime(11) = 31 and prime(3) = 5, and floor(31/5) = 6. %o A287920 (PARI) T(n,k) = prime(n)\prime(k); %o A287920 tabl(nn) = for (n=1, nn, for (k=1, n, print1(T(n, k), ", ")); print()); \\ _Michel Marcus_, Jun 06 2017 %Y A287920 Cf. A000040 (primes), A130290 (1st column), A144769 (2nd column), A116572 (3rd column). %K A287920 nonn,tabl %O A287920 1,4 %A A287920 _Bob Selcoe_, Jun 02 2017