OFFSET
1,2
COMMENTS
This sequence is a permutation of the natural numbers:
- necessarily some nonzero digit, say d, appears infinitely many times,
- if d=1, then we have infinitely many multiples of 1, and eventually every number will show up,
- if d>1, then all the multiples of d will show up, as there are infinitely many multiples of d containing a "1" digit, we have infinitely many multiples of 1 as well, and eventually every number will show up.
This sequence can also be seen as an irregular table, where the n-th has A055640(a(n)) terms, and T(n, k) is a multiple of the k-th nonzero digit of a(n).
LINKS
EXAMPLE
For first terms and corresponding digits are:
n a(n) n-th digit
-- ---- ----------
1 1 1
2 2 2
3 3 3
4 4 4
5 5 5
6 6 6
7 7 7
8 8 8
9 9 9
10 10 1
11 11 1
12 12 1
13 13 1
14 14 2
PROG
(PARI) See Links section.
CROSSREFS
KEYWORD
AUTHOR
Rémy Sigrist, Jan 07 2020
STATUS
approved