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A157420
a(0)=1. a(n) = the smallest integer coprime to a(n-1) and greater than the n-th Fibonacci number.
4
1, 2, 3, 4, 5, 6, 11, 14, 23, 35, 57, 91, 145, 234, 379, 611, 989, 1598, 2587, 4182, 6767, 10947, 17713, 28658, 46371, 75026, 121395, 196421, 317812, 514233, 832042, 1346271, 2178310, 3524579, 5702889, 9227467, 14930353, 24157818, 39088171
OFFSET
0,2
LINKS
EXAMPLE
a(7) = 14, and the 8th Fibonacci number is 21. So for a(8) we want the smallest integer that is both coprime to 14 and is > 21. Checking: 22 is not coprime to 14. But 23 is coprime to 14, so a(8) = 23.
MATHEMATICA
Fold[Append[#1, Block[{k = Fibonacci@ #2 + 1}, While[! CoprimeQ[k, #1[[-1]] ], k++]; k]] &, {1}, Range@ 38] (* Michael De Vlieger, Oct 30 2017 *)
CROSSREFS
Sequence in context: A309548 A088411 A075073 * A221471 A058243 A264665
KEYWORD
nonn
AUTHOR
Leroy Quet, Feb 28 2009
EXTENSIONS
Extended by Ray Chandler, Jun 19 2009
STATUS
approved