OFFSET
0,2
COMMENTS
If S, T, U are infinite sequences, zip_2(S,T) means the perfect shuffle S_0, T_0, S_1, T_1, S_2, ... and similarly zip_3(S,T,U) means S_0, T_0, U_0, S_1, ...
The colon means "concatenate".
Endrullis et al. define the sequence over the alphabet {a,b}, getting abbbbabbbbabbababbbbabbbbbabbbabbbbababaabbababbbbbba...
(see also A225181).
LINKS
N. J. A. Sloane, Table of n, a(n) for n = 0..8191
Jörg Endrullis, Clemens Grabmayer, Dimitri Hendriks, Mix-Automatic Sequences, slides of talk presented at workshop on challenges in combinatorics on words, Fields Institute, Toronto, April 21-26, 2013.
Jörg Endrullis, Clemens Grabmayer, Dimitri Hendriks, Mix-Automatic Sequences, In: Proceedings Conference on Language and Automata Theory and Applications (LATA 2013), Springer, 2013, pages 262-274.
EXAMPLE
The initial steps in the calculation are:
M := [a]
X := [b]
Y := [b]
X = [b, b, b]
Y = [b, a, b, b]
M = [a, b, b, b]
X = [b, b, b, b, a, b, b]
Y = [b, a, b, b, b, a, a, b, b, b, b, b, b]
M = [a, b, b, b, b, a, b, b]
X = [b, b, b, b, a, b, b, b, b, a, b, b, a, b, a]
Y = [b, a, b, b, b, a, a, b, b, b, b, b, b, b, b, b, a, a, a, b, a, a, b, b, b]
M = [a, b, b, b, b, a, b, b, b, b, a, b, b, a, b, a]
...
MAPLE
M1:=7;
M:=[a]; X:=[b]; Y:=[b];
for n from 1 to M1 do
l1:=min(nops(X), nops(Y));
t1:=[b];
for i1 from 1 to l1 do
t1:=[op(t1), X[i1], Y[i1]]; od:
X:=t1;
#lprint("X = ", X);
l2:=min(nops(M), nops(Y));
t2:=[b];
for i2 from 1 to l2 do
t2:=[op(t2), M[i2], Y[i2], Y[i2]]; od:
Y:=t2;
#lprint("Y = ", Y);
M:=[a, op(X)];
#lprint("M = ", M);
od:
M;
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 03 2013
STATUS
approved