OFFSET
1,2
COMMENTS
The number of n-digit terms is (n^4+22n^3+95n^2+98n)/24. - David Wasserman
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
for i from 1 to 9 do g(i):= [seq(t, t=0..9, i)] od: g(0):= [0]:
A[1]:= [$1..9]:
for d from 2 to 4 do A[d]:= map(t -> op(10*t+~g(t mod 10)), A[d-1]) od:
map(op, [seq(A[d], d=1..4)]); # Robert Israel, Sep 01 2019
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Jun 26 2004
EXTENSIONS
Edited by David Wasserman, Dec 28 2005
STATUS
approved