A173459 a(n) = A173457(n+1)/4.

2, 3, 1, 7, 9, 1, 7, 9, 3, 21, 27, 1, 7, 9, 3, 21, 27, 3, 21, 27, 9, 63, 81, 1, 7, 9, 3, 21, 27, 3, 21, 27, 9, 63, 81, 3, 21, 27, 9, 63, 81, 9, 63, 81, 27, 189, 243, 1, 7, 9, 3, 21, 27, 3, 21, 27, 9, 63, 81, 3, 21, 27, 9, 63, 81, 9, 63, 81, 27, 189, 243, 3

Offset: 1

Author

Omar E. Pol, Feb 18 2010

Keywords

• nonn
• tabf

Examples

			From Omar E. Pol, Apr 22 2013 (Start):
When written as an irregular triangle begins:
2,3;
1,7,9;
1,7,9,3,21,27;
1,7,9,3,21,27,3,21,27,9,63,81;
1,7,9,3,21,27,3,21,27,9,63,81,3,21,27,9,63,81,9,63,81,27,189,243;
1,7,9,3,21,27,3,21,27,9,63,81,3,21,27,9,63,81,9,63,81,27,189,243,3,...
(End)
		

Links

• David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
• N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Crossrefs

Cf. A173456, A173457, A173458, A173463.

Extensions

a(13)-a(72) from Lars Blomberg, Apr 22 2013