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

1,2

Links

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

Example

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

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 *)

Crossrefs

Cf. A084409, A084410, A084411.

Sequence in context: A179335 A330994 A097858 * A257347 A143345 A111679

Adjacent sequences: A084405 A084406 A084407 * A084409 A084410 A084411

Keyword

nonn,easy,tabl

Author

Amarnath Murthy, Jun 01 2003

Extensions

Edited and extended by David Wasserman, Dec 27 2004

Status

approved