OFFSET
1,1
COMMENTS
The complement of 0 is 9, of 1 is 8, of 2 is 7, etc. All terms of the sequence have an even number of digits, and all terms are divisible by 9.
LINKS
Jean-Marc Falcoz, Table of n, a(n) for n = 1..3000
EXAMPLE
18 produces 81 when 1 is replaced by 8 and 8 is replaced by 1; 18 and 81 use the same set of digits, in a different order.
1089 produces 8910 when 1 is replaced by 8, 0 by 9, 8 by 1 and 9 by 0; 1089 and 8910 use the same set of digits, in a different order.
PROG
(PARI) replace_digits(n) = my(d=digits(n)); for(k=1, #d, d[k]=abs(d[k]-9)); d
is(n) = vecsort(digits(n))==vecsort(replace_digits(n)) \\ Felix Fröhlich, Feb 14 2018
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini and Jean-Marc Falcoz, Feb 14 2018
STATUS
approved