OFFSET
1,5
COMMENTS
This sequence has fractal features; apparently, for any k > 0, the first k terms are repeated later (see illustration in Links section).
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..10000
Rémy Sigrist, Logarithmic scatterplot of the first 80000 terms (the two colored sections are equal up to an horizontal shift)
EXAMPLE
The first terms, alongside the corresponding k's, are:
n a(n) k's
--- ------- ---------
1 1 {}
2 1 {}
3 1 {1}
4 1 {1}
5 2 {1, 2}
6 2 {2}
7 3 {1, 3}
8 1 {}
9 1 {}
10 1 {1}
11 1 {1}
12 8 {1, 2, 4}
13 10 {2, 5}
14 90 {3, 5, 6}
15 42 {6, 7}
16 42 {6, 7}
17 56 {1, 7, 8}
PROG
(PARI) for (n=1, #(a=vector(60)), print1 (a[n] = prod(k=1, (n-1)\2, if (a[n-k]==a[n-2*k], k, 1)) ", "))
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Rémy Sigrist, Nov 10 2019
STATUS
approved