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Number of grid points that are covered after n-th stage of A139250 version "Tree", starting with a(0) = 1 and assuming the toothpicks have length 4, 3, and 2.
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%I #19 Feb 19 2018 22:02:25

%S 1,5,13,25,37,53,81,113,133,149,177,213,253,313,401,481,517,533,561,

%T 597,637,697,785,869,925,985,1077,1189,1329,1537,1793,1985,2053,2069,

%U 2097,2133,2173,2233,2321,2405,2461,2521,2613,2725,2865,3073,3329,3525,3613

%N Number of grid points that are covered after n-th stage of A139250 version "Tree", starting with a(0) = 1 and assuming the toothpicks have length 4, 3, and 2.

%C The first differences give A147646.

%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) = 1 + 4*A153006(n) = 1 + A159795(n).

%Y Cf. A139250, A152980, A153006, A147646, A159795, A160128, A160420, A160422, A160425, A182618, A194800, A194802.

%K nonn

%O 0,2

%A _Omar E. Pol_, Oct 24 2011