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A124071
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a(1)=1. a(n) = GCD(n,a(n-1)) + GCD(n+1,a(n-1)).
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1, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 4, 5, 2, 3, 4, 5, 6, 5, 2, 3, 4, 3, 4, 5, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 4, 5, 6, 7, 8, 5, 6, 5, 2, 3, 4, 3, 4, 5, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 4, 5, 6, 7, 2, 3, 4, 3, 2, 3, 4, 3, 4, 5, 2, 3, 4, 5, 6, 5, 2, 3, 4, 3, 4, 5, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 4, 5, 6, 7, 2, 3, 4, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| First occurrence of k: 1, 2, 3, 6, 7, 20, 41, 42, 127, 1304, 1809, 2530, 2531, 42132, 113413, 113414, 196575, 3160096, 3160097, 3160098, 3160099, 3160100, 3160101, ..., . Robert G. Wilson v Nov 07 2006.
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MAPLE
| a[1]:=1: for n from 2 to 130 do a[n]:=gcd(n, a[n-1])+gcd(n+1, a[n-1]) od: seq(a[n], n=1..130); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 06 2006
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MATHEMATICA
| a[1] = 1; a[n_] := a[n] = GCD[n, a[n - 1]] + GCD[n + 1, a[n - 1]]; Array[a, 105] (* Robert G. Wilson v *)
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CROSSREFS
| Sequence in context: A173540 A070770 A071487 * A034697 A110157 A178493
Adjacent sequences: A124068 A124069 A124070 * A124072 A124073 A124074
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Nov 05 2006
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Robert G. Wilson v, Nov 06 2006
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