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A163578
If n is prime, a(n) is next composite greater than a(n-1), else if n is composite, a(n) is next prime greater than a(n-1) else 2.
1
2, 4, 6, 7, 8, 11, 12, 13, 17, 19, 20, 23, 24, 29, 31, 37, 38, 41, 42, 43
OFFSET
1,1
EXAMPLE
1 is not prime, a(1)=2, 2 is prime, a(2)=4, 3 is prime, a(3)=6, 4 is composite, a(4)=7.
CROSSREFS
Sequence in context: A165778 A286066 A139527 * A345918 A269389 A092054
KEYWORD
nonn
AUTHOR
Gerald Hillier, Jul 31 2009
STATUS
approved