OFFSET
0,2
FORMULA
1->{2}, 2->{1, 2, 3, 4}, 3->{2, 4}, 4->{2, 3}
MATHEMATICA
s[1] = {2}; s[2] = {1, 2, 3, 4}; s[3] = {2, 4}; s[4] = {2, 3}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]] aa = p[6]
CROSSREFS
KEYWORD
nonn,uned
AUTHOR
Roger L. Bagula, May 27 2005
STATUS
approved