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Search: id:A084663
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| A084663 |
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a(1) = 8; a(n) = a(n-1) + gcd(a(n-1), n). |
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+0
6
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| 8, 10, 11, 12, 13, 14, 21, 22, 23, 24, 25, 26, 39, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 87, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 177, 180, 181, 182, 189, 190
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The first 150000000 differences are all primes or 1. Is this true in general?
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REFERENCES
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Eric S. Rowland, A simple prime-generating recurrence, Abstracts Amer. Math. Soc., 29 (No. 1, 2008), p. 50 (Abstract 1035-11-986).
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
Eric S. Rowland, A simple prime-generating recurrence.
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MAPLE
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S := 8; f := proc(n) option remember; global S; if n=1 then S else f(n-1)+igcd(n, f(n-1)); fi; end;
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MATHEMATICA
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f[n_] := f[n-1] + GCD[n, f[n-1]]; f[1]=8
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CROSSREFS
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Cf. A084662, A106108.
Sequence in context: A031953 A043697 A043425 this_sequence A031037 A006757 A126803
Adjacent sequences: A084660 A084661 A084662 this_sequence A084664 A084665 A084666
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KEYWORD
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nonn
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AUTHOR
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Matthew Frank (mfrank(AT)wopr.wolfram.com) on behalf of the 2003 New Kind of Science Summer School, Jul 15 2003
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