A103684 Triangle read by rows, based on the morphism f: 1->{1,2}, 2->{1,3}, 3->{1}. First row is 1. If current row is a,b,c,..., then the next row is a,b,c,...,f(a),f(b),f(c),...

1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 1, 2, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 3, 1, 2, 1, 1, 2, 1, 3, 1, 2, 1, 1, 2, 1, 3, 1

Offset

1,4

Links

G. C. Greubel, Table of n, a(n) for the first 8 rows, flattened

Example

[1], [1,1,2], [1,1,2,1,2,1,2,1,3], [1,1,2,1,2,1,2,1,3,1,2,1,2,1,3,1,2,1,3,1,2,1,3,1,2,1], ...

Mathematica

NestList[ Flatten[ Join[ #, # /. {1 -> {1, 2}, 2 -> {1, 3}, 3->{1}}]] &, {1}, 4] // Flatten (* Robert G. Wilson v, Jul 09 2006 - corrected by G. C. Greubel, Oct 26 2017 *)

Prog

(PARI) {a(n)=local(m, v, w); v=w=[1]; while(length(w)<n, m=length(v); for(k=1, m, v=concat(v, [[1, 2], [1, 3], [1]][v[k]])); w=concat(w, v)); w[n]} /* Michael Somos, Apr 16 2005 */

Crossrefs

Cf. A073058, A103685, A103682.

Sequence in context: A061337 A352767 A253051 * A105103 A086669 A357906

Adjacent sequences: A103681 A103682 A103683 * A103685 A103686 A103687

Keyword

nonn,tabf

Author

Roger L. Bagula, Mar 26 2005

Extensions

Image of {3} in the definition corrected by R. J. Mathar, Nov 18 2010

Status

approved