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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. 4
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 (list; table; graph; refs; listen; history; text; internal format)
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: A087173 A179335 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

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Last modified October 15 01:40 EDT 2019. Contains 328025 sequences. (Running on oeis4.)