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A326791
For n > 1, let f_n be the lexicographically earliest sequence of distinct positive terms such that f_n(1) = 1, f_n(2) = n, and for k > 2, f_n(k) divides f_n(k-2) + f_n(k-1); if f_n is finite, then a(n) is the number of terms of f_n, otherwise a(n) = -1; a(1) = 1.
1
1, 39, 23, 5, 10, 9, 31, 8, 8, 8, 7, 8, 7, 9, 10, 29, 9, 38, 36, 13, 14, 13, 8, 12, 40, 19, 11, 25, 10, 15, 13, 18, 11, 5, 39, 36, 40, 37, 12, 25, 11, 12, 29, 30, 33, 25, 32, 5, 40, 25, 12, 25, 11, 21, 40, 27, 18, 19, 17, 9, 41, 18, 11, 5, 41, 37, 40, 12, 29
OFFSET
1,2
COMMENTS
Apparently, f_n is finite for any n > 0.
The first records are:
n a(n)
------- ----
1 1
2 39
25 40
61 41
78 45
266 47
279 56
629 102
95417 103
331468 104
1318090 108
5383290 109
EXAMPLE
For n = 2:
- f_2 corresponds to A085947 which is finite with 39 terms,
- hence a(2) = 39.
PROG
(PARI) See Links section.
CROSSREFS
Cf. A085947.
Sequence in context: A196092 A196089 A033359 * A374870 A268854 A317388
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Oct 19 2019
STATUS
approved