login
A287920
Triangle T(n,k) read by rows: T(n,k) = floor(prime(n)/prime(k)), n >= k >= 1.
0
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
1,4
COMMENTS
Alternate name: triangle of quotients of prime(n)/prime(k), n >= k >= 1.
EXAMPLE
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.
PROG
(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
CROSSREFS
Cf. A000040 (primes), A130290 (1st column), A144769 (2nd column), A116572 (3rd column).
Sequence in context: A225640 A345418 A194543 * A027293 A104762 A152462
KEYWORD
nonn,tabl
AUTHOR
Bob Selcoe, Jun 02 2017
STATUS
approved