A084408 Triangle read by rows: if n is prime, row n contains the n smallest primes not already used; if n is composite, row n contains the n smallest composite numbers not already used. A permutation of the positive integers.

1, 2, 3, 5, 7, 11, 4, 6, 8, 9, 13, 17, 19, 23, 29, 10, 12, 14, 15, 16, 18, 31, 37, 41, 43, 47, 53, 59, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 55, 56, 57, 58, 60

Offset: 1

Author

Amarnath Murthy, Jun 01 2003

Keywords

• nonn
• easy
• tabl

Examples

			1
2 3
5 7 11
4 6 8 9
13 17 19 23 29
10 12 14 15 16 18
...
		

Links

• Ivan Neretin, Table of n, a(n) for n = 1..8001

Crossrefs

Cf. A084409, A084410, A084411.

Programs

Mathematica

a = {1}; Do[a = Join[a, Take[Select[Complement[Range[Prime[PrimePi@Max@a + n]], a], ! (PrimeQ[#] \[Xor] PrimeQ[n]) &], n]], {n, 2, 12}]; a (* Ivan Neretin, May 23 2018 *)

Extensions

Edited and extended by David Wasserman, Dec 27 2004