OFFSET
1,2
COMMENTS
The sequence starts with a(1) = 1 and is always extended with the smallest integer not yet used that doesn't lead to a contradiction.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
The pair (1,2) uses only one odd digit (1);
the pair (2,3) uses only one odd digit (3);
the pair (3,4) uses only one odd digit (3);
the pair (4,5) uses only one odd digit (5);
the pair (5,6) uses only one odd digit (5);
the pair (6,7) uses only one odd digit (7);
the pair (7,8) uses only one odd digit (7);
the pair (8,9) uses only one odd digit (9);
the pair (9,20) uses only one odd digit (9);
the pair (20,10) uses only one odd digit (1);
the pair (10,22) uses only one odd digit (1);
etc.
MAPLE
a:= 0: b:= 0: Res:= NULL:
for i from 1 to 100 do
for t from a+1 while nops(select(type, convert(t, base, 10), odd))<> 1 do
od;
a:= t;
for t from b+1 while nops(select(type, convert(t, base, 10), odd))>0 do
od;
b:= t;
Res:= Res, a, b;
od:
Res; # Robert Israel, Nov 03 2017
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Eric Angelini, Aug 08 2016
STATUS
approved