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

1,4

Comments

Alternate name: triangle of quotients of prime(n)/prime(k), n >= k >= 1.

Links

Table of n, a(n) for n=1..91.

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

Adjacent sequences: A287917 A287918 A287919 * A287921 A287922 A287923

Keyword

nonn,tabl

Author

Bob Selcoe, Jun 02 2017

Status

approved