A222173 - OEIS

%I #15 Mar 24 2013 14:01:30

%S 0,1,1,1,2,3,2,1,2,4,4,3,5,7,4,1,2,4,6,8

%N Number of pentagons added at n-th stage to the structure of A222172.

%C Essentially the first differences of A222172.

%C Also number of P-toothpicks added at n-th stage to the P-toothpick structure of A222172.

%C First differs from A152978 at a(9).

%H N. J. A. Sloane, <a href="/wiki/Catalog_of_Toothpick_and_CA_Sequences_in_OEIS">Catalog of Toothpick and Cellular Automata Sequences in the OEIS</a>

%H <a href="/index/To#toothpick">Index entries for sequences related to toothpick sequences</a>

%F a(n) = A222181(n+2)/10 = A222177(n+1)/2, n >= 1.

%e Apparently this is an irregular triangle:

%e 0;

%e 1, 1;

%e 1, 2, 3, 2;

%e 1, 2, 4, 4, 3, 5, 7, 4;

%e 1, 2, 4, 6, 8,...

%Y Cf. A139251, A152978, A222172, A222177, A222180, A222181.

%K nonn,tabf,more

%O 0,5

%A _Omar E. Pol_, Mar 21 2013