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A343505
a(n) is the least common multiple of the nonzero digits in factorial base expansion of 1/n.
2
1, 1, 2, 2, 4, 1, 6, 3, 6, 2, 60, 2, 120, 3, 3, 6, 1008, 4, 51480, 1, 4, 30, 6930, 1, 140, 36, 60, 20, 16380, 4, 243374040, 12, 105, 504, 12, 6, 6126120, 4680, 168, 3, 314954640, 10, 209969760, 24, 4, 180180, 1790848659600, 6, 924, 6, 660, 1260, 8303710615200
OFFSET
1,3
COMMENTS
See the Wikipedia link for the construction method of 1/n in factorial base.
EXAMPLE
The first terms, alongside 1/n in factorial base, are:
n a(n) 1/n in factorial base
-- ----- -----------------------------------------
1 1 1
2 1 0.1
3 2 0.0 2
4 2 0.0 1 2
5 4 0.0 1 0 4
6 1 0.0 1
7 6 0.0 0 3 2 0 6
8 3 0.0 0 3
9 6 0.0 0 2 3 2
10 2 0.0 0 2 2
11 60 0.0 0 2 0 5 3 1 4 0 10
12 2 0.0 0 2
13 120 0.0 0 1 4 1 2 5 4 8 5 0 12
14 3 0.0 0 1 3 3 3
15 3 0.0 0 1 3
16 6 0.0 0 1 2 3
17 1008 0.0 0 1 2 0 2 3 6 8 9 0 9 2 7 0 16
18 4 0.0 0 1 1 4
19 51480 0.0 0 1 1 1 6 2 0 9 5 2 6 11 11 13 8 0 18
20 1 0.0 0 1 1
PROG
(PARI) a(n) = my (v=1, f=1/n); for (r=2, oo, if (f==0, return (v), floor(f), v=lcm(v, floor(f))); f=frac(f)*r)
CROSSREFS
KEYWORD
nonn,look,base
AUTHOR
Rémy Sigrist, Apr 17 2021
STATUS
approved