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A211029
Triangle read by rows in which row n lists the binary words of length n over the alphabet {1,2} with no initial repeats.
4
1, 2, 12, 21, 121, 122, 211, 212, 1211, 1221, 1222, 2111, 2112, 2122, 12111, 12112, 12211, 12212, 12221, 12222, 21111, 21112, 21121, 21122, 21221, 21222, 121111, 121112, 121122, 122111, 122112, 122121, 122211, 122212, 122221, 122222, 211111, 211112
OFFSET
1,2
COMMENTS
As usual in the OEIS, binary alphabets are encoded with {1,2} over the alphabet {0,1} the entries contain nonzero "numbers" beginning with 0.
EXAMPLE
The fourth row of triangle of binary sequences is
0100, 0110, 0111, 1000, 1001, 1011 (see section example of A122536) therefore the fourth row of this triangle is
1211, 1221, 1222, 2111, 2112, 2122.
The first six rows of triangle are:
1, 2;
12, 21;
121, 122, 211, 212;
1211, 1221, 1222, 2111, 2112, 2122;
12111, 12112, 12211, 12212, 12221, 12222, 21111, 21112, 21121, 21122, 21221, 21222;
121111, 121112, 121122, 122111, 122112, 122121, 122211, 122212, 122221, 122222, 211111, 211112, 211121, 211122, 211212, 211221, 211222, 212211, 212221, 212222;
MAPLE
s:= proc(n) s(n):= `if`(n=0, [[]], map(x->
[[x[], 1], [x[], 2]][], s(n-1))) end:
T:= proc(n) map(x-> parse(cat(x[])), select(proc(l) local i;
for i to iquo(nops(l), 2) do if l[1..i]=l[i+1..2*i]
then return false fi od; true end, s(n)))[] end:
seq(T(n), n=1..7); # Alois P. Heinz, Dec 02 2012
CROSSREFS
Row n has length A122536(n).
Sequence in context: A199986 A336528 A077410 * A225188 A193828 A191226
KEYWORD
nonn,tabf
AUTHOR
Omar E. Pol, Nov 29 2012
EXTENSIONS
More terms and name improved by R. J. Mathar, Nov 30 2012
STATUS
approved