OFFSET
0,2
LINKS
E. Barcucci, A. Bernini, S. Bilotta, R. Pinzani, Cross-bifix-free sets in two dimensions, arXiv preprint arXiv:1502.05275 [cs.DM], 2015.
S. Bilotta, E. Pergola and R. Pinzani, A new approach to cross-bifix-free sets, arXiv preprint arXiv:1112.3168 [cs.FL], 2011.
T. Harju and D. Nowotka, Border correlation of binary words.
P. Tolstrup Nielsen, A note on bifix-free sequences, IEEE Trans. Info. Theory IT-19 (1973), 704-706.
FORMULA
a(2n+1) = 4a(2n); a(2n) = 4a(2n-1) - a(n).
MATHEMATICA
a[0]=1; a[n_]:=a[n]=4*a[n-1]-If[EvenQ[n], a[n/2], 0] (* Ed Pegg Jr, Jan 05 2005 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved