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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 (list; table; graph; refs; listen; history; text; internal format)
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: A112739 A225640 A194543 * A027293 A104762 A152462

Adjacent sequences:  A287917 A287918 A287919 * A287921 A287922 A287923

KEYWORD

nonn,tabl

AUTHOR

Bob Selcoe, Jun 02 2017

STATUS

approved

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Last modified June 25 07:53 EDT 2019. Contains 324347 sequences. (Running on oeis4.)