OFFSET
1,1
EXAMPLE
1 --> 11, 2 --> 22, 3 --> 33, ..., 9 --> 99, 10 --> 101, 11 --> 112, 12 --> 123,
..., 18 --> 189, 19 --> 1910 (ouch!), 20 --> 202, 21 --> 213, ...
MATHEMATICA
f[n_] := FromDigits[ Join[ IntegerDigits[ n], IntegerDigits[Plus @@ IntegerDigits[ n]] ]]; t = {}; Do[t = Union[AppendTo[t, f[n]]], {n, 10^6}]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Robert G. Wilson v, Jun 15 2005
EXTENSIONS
a(55) from Rémy Sigrist, May 16 2019
STATUS
approved