A331959 a(n) is the greatest prime number of the form floor(n/k) where k > 0.

2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 3, 13, 7, 7, 5, 17, 3, 19, 5, 7, 11, 23, 3, 5, 13, 13, 7, 29, 7, 31, 5, 11, 17, 17, 7, 37, 19, 19, 13, 41, 7, 43, 11, 11, 23, 47, 5, 7, 7, 17, 17, 53, 13, 13, 11, 19, 29, 59, 7, 61, 31, 31, 7, 13, 13, 67, 17, 23, 23, 71, 7, 73

Offset

2,1

Links

Rémy Sigrist, Table of n, a(n) for n = 2..10000

Formula

a(n) = floor(n/A331954(n)).

a(p) = p for any prime number p.

a(2*p) = p for any prime number p.

Example

For n = 8:
- floor(8/1) = 8 is not a prime number,
- floor(8/2) = 4 is not a prime number,
- floor(8/3) = 2 is a prime number,
- hence a(8) = 2.

Prog

(PARI) a(n) = for (k=1, oo, if (isprime(n\k), return (n\k)))

Crossrefs

Cf. A331954.

Sequence in context: A327398 A323616 A102095 * A109395 A145254 A379120

Adjacent sequences: A331956 A331957 A331958 * A331960 A331961 A331962

Keyword

nonn

Author

Rémy Sigrist, Feb 02 2020

Status

approved