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Search: id:A080220
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| A080220 |
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a(1)=2; then if n is prime, a(n) is the smallest prime number greater than a(n-1), if n is composite a(n)=a(n-1)+1. |
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+0
1
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| 2, 3, 5, 6, 7, 8, 11, 12, 13, 14, 17, 18, 19, 20, 21, 22, 23, 24, 29, 30, 31, 32, 37, 38, 39, 40, 41, 42, 43, 44, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 59, 60, 61, 62, 63, 64, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 97
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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More generally, let b(1)>1, m >0, b(n) be the smallest integer > b(n-1) such that b(n) is prime if n is prime, then limit n ->infinity b(n)/n =L exists and b<L<b+1.
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FORMULA
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There is a constant C such that limit n ->infinity a(n)/n = C =1.72...
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PROGRAM
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(PARI) a(n)=if(n<2, 2, if(isprime(n), nextprime(a(n-1)+1), a(n-1)+1)
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CROSSREFS
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Sequence in context: A096600 A122686 A161873 this_sequence A028778 A094180 A116545
Adjacent sequences: A080217 A080218 A080219 this_sequence A080221 A080222 A080223
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 06 2003
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