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A121730 a(n) = the smallest positive integer which does not occur earlier in the sequence and which is coprime to the n-th Fibonacci number. 2
1, 2, 3, 4, 6, 5, 7, 8, 9, 12, 10, 11, 13, 14, 17, 16, 15, 21, 18, 19, 23, 20, 22, 25, 24, 26, 27, 28, 29, 37, 30, 31, 33, 32, 34, 35, 36, 38, 39, 43, 40, 41, 42, 44, 47, 45, 46, 53, 48, 49, 51, 50, 52, 55, 54, 59, 57, 56, 58, 67, 60, 61, 63, 62, 64, 65, 66, 68, 69, 72, 70, 71 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Sequence is a permutation of the positive integers.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

55 is the 10th Fibonacci number. Among those positive integers not occurring among the first 9 terms of the sequence, 12 is the smallest which is coprime to 55, so a(10) = 12. 10 and 11 also do not occur among the first 9 terms of the sequence, but they are not coprime to 55.

MAPLE

L:= [$1..100]: # for all terms before the first term > 100

for n from 1 do

  v:= combinat:-fibonacci(n);

  found:= false;

  for j from 1 to nops(L) do

    if igcd(L[j], v)=1 then

      A[n]:= L[j];

      L:= subsop(j=NULL, L);

      found:= true;

      break

    fi;

  od;

  if not found then break fi

od:

seq(A[i], i=1..n-1); # Robert Israel, Jun 26 2018

CROSSREFS

Cf. A000045, A121731.

Sequence in context: A130946 A073284 A057511 * A275659 A244321 A062894

Adjacent sequences:  A121727 A121728 A121729 * A121731 A121732 A121733

KEYWORD

nonn

AUTHOR

Leroy Quet, Aug 18 2006

EXTENSIONS

Extended by Ray Chandler, Aug 22 2006

STATUS

approved

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Last modified January 20 02:05 EST 2019. Contains 319320 sequences. (Running on oeis4.)