A287920 Triangle T(n,k) read by rows: T(n,k) = floor(prime(n)/prime(k)), n >= k >= 1.
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, 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, 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
Offset: 1
Examples
Triangle starts: n/k 1 2 3 4 5 6 7 8 9 10 11 12 1 1 2 1 1 3 2 1 1 4 3 2 1 1 5 5 3 2 1 1 6 6 4 2 1 1 1 7 8 5 3 2 1 1 1 8 9 6 3 2 1 1 1 1 9 11 7 4 3 2 1 1 1 1 10 14 9 5 4 2 2 1 1 1 1 11 15 10 6 4 2 2 1 1 1 1 1 12 18 12 7 5 3 2 2 1 1 1 1 1 T(11,3) = 6 because prime(11) = 31 and prime(3) = 5, and floor(31/5) = 6.
Programs
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PARI
T(n,k) = prime(n)\prime(k); tabl(nn) = for (n=1, nn, for (k=1, n, print1(T(n, k), ", ")); print()); \\ Michel Marcus, Jun 06 2017
Comments