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A213277
a(n) is the length of the cycle of first differences of k such that Fibonacci(k) mod n = k mod n.
2
3, 8, 3, 8, 6, 16, 3, 8, 14, 10, 4, 28, 24, 16, 3, 36, 6, 18, 11, 16, 15, 48, 3, 18, 42, 8, 12, 14, 14, 30, 3, 40, 18, 32, 4, 76, 9, 56, 11, 40, 12, 88, 15, 16, 24, 32, 3, 16, 34, 24, 21, 108, 6, 8, 6, 24, 21, 58, 12, 60, 15, 16, 3, 56, 30, 136, 9, 16, 56
OFFSET
2,1
COMMENTS
In calculating the terms, a set of values A that is found twice (AA) is not enough to be certain that A is a cycle since the continuation may be AAA..AAABAAA..AAAB where B is a different set of values. In calculating the data above, a cycle is accepted when it has occurred 10 times in a row.
LINKS
EXAMPLE
Example with n=3:
Fib(k): 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, ...
Fib(k) mod 3: 0,1,1,2,0,2,2,1,0,1,1,2,0,2,2,1,0,1,1,2,0,2,2,1,0
k mod 3: 0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0,1,2,0
Accepted k values indicated by x:
x,x,-,-,-,x,-,x,-,-,x,x,x,-,-,-,-,-,-,-,-,-,-,-,x
Accepted k values: 0, 1, 5, 7, 10, 11, 12, 14, 24
First differences of k values: 1, 4, 2, 3, 1, 1, 2, 10
After this the cycle repeats, so a(3) = 8.
CROSSREFS
Sequence in context: A010706 A204998 A019919 * A135608 A106230 A205126
KEYWORD
nonn
AUTHOR
Lars Blomberg, Jun 08 2012
STATUS
approved