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 A105316 Null vertex tetrahedron digraph 4-symbol substitution : characteristic polynomial: x^4-x. Each edge is taken only once. 0
 1, 1, 2, 3, 1, 2, 3, 2, 3, 3, 4, 1, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 1, 3, 1, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 1, 3, 2, 3, 3, 4, 3, 4, 1, 3, 3, 4, 1, 3, 1, 3, 2, 3, 1, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 1, 3, 2, 3, 3, 4, 3, 4, 1, 3, 3, 4, 1, 3, 1, 3, 2, 3, 2, 3, 3, 4, 3, 4, 1, 3, 3, 4, 1, 3, 1, 3, 2, 3, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS There are four matrix isomers of these and they are equivalent in polynomials to the substitution: 1-> {2,3,4} 2->{3} 3->{4} 4->{1} of which there are also four kinds. LINKS FORMULA 1->{2, 3}, 2->{3, 4}, 3->{}, 4->{1, 4} MATHEMATICA s[1] = {2, 3}; s[2] = {3, 4}; s[3] = {}; s[4] = {1, 4}; t[a_] := Join[a, Flatten[s /@ a]]; p[0] = {1}; p[1] = t[{1}]; p[n_] := t[p[n - 1]] aa = Flatten[Table[p[n], {n, 0, 6}]] CROSSREFS Sequence in context: A194899 A228094 A059832 * A105933 A105315 A328912 Adjacent sequences:  A105313 A105314 A105315 * A105317 A105318 A105319 KEYWORD nonn AUTHOR Roger L. Bagula, Apr 25 2005 STATUS approved

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Last modified December 2 04:43 EST 2021. Contains 349437 sequences. (Running on oeis4.)