OFFSET
0,3
COMMENTS
All terms are distinct, but certain terms (see A109682) are missing.
For the terms 3^k-1 (all 2's in ternary), the diagonal is not started at the leading 2, but at the leading 1 of the following term. - Georg Fischer, Mar 13 2020
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..10000
Georg Fischer, Perl program
EXAMPLE
number diagonal decimal
0 0 0
1 1 1
2 12 5
10 10 3
11 11 4
12 22 8
20 20 6
21 121 16
22 102 11
100 100 9
101 101 10
102 112 14
110 110 12
11. ... ...
1.
.
MAPLE
t:= (n, i)-> (d-> `if`(i=0, d, t(m, i-1)))(irem(n, 3, 'm')):
b:= (n, i)-> `if`(3^i>n, 0, t(n, i) +3*b(n+1, i+1)):
a:= n-> b(n, 0):
seq(a(n), n=0..100); # Alois P. Heinz, Mar 13 2020
PROG
(Haskell)
a109681 n = a109681_list !! n
a109681_list = map (foldr (\d v -> 3 * v + d) 0) $ f a030341_tabf where
f vss = (g 0 vss) : f (tail vss)
g k (ws:wss) = if k < length ws then ws !! k : g (k + 1) wss else []
-- Reinhard Zumkeller, Nov 19 2013
(Perl) Cf. link.
CROSSREFS
KEYWORD
nonn,nice,easy,base
AUTHOR
Philippe Deléham, Aug 08 2005
EXTENSIONS
Conjectured g.f. and recurrence removed by Georg Fischer, Mar 13 2020
STATUS
approved