A096221 a(n) is the number of distances used by minimal prime-complete rulers for the first n primes.

1, 2, 3, 5, 7, 10, 13, 15, 18

Offset

0,2

Comments

The best known upper bounds for a(9-15) are 22, 25, 29, 33, 37, 41, 45. See attached file for the corresponding rulers. - Dmitry Kamenetsky, Mar 09 2018

Links

Table of n, a(n) for n=0..8.

Dmitry Kamenetsky, Upper bounds and their rulers for a(9-15)

Carlos Rivera, The Prime Puzzles & Problems Connection: Puzzle 172.

Carlos Rivera, The Prime Puzzles & Problems Connection: Puzzle 914.

Example

a(7)=15: there are 7 primes (2, 3, 5, 7, 11, 13, 17) and 8 ones. These rulers can generate every distance between 1 and 66, inclusive. There are two such rulers: 1.1.1.1.11.1.1.2.13.7.17.1.3.5.1 and 1.1.1.1.11.2.1.1.13.7.17.1.5.3.1

Crossrefs

Sequence in context: A090420 A162999 A064509 * A258084 A120367 A072831

Adjacent sequences: A096218 A096219 A096220 * A096222 A096223 A096224

Keyword

nonn,more

Author

Ray G. Opao, Jul 29 2004

Status

approved