A287920 - OEIS

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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

(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: 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