

A220745


"Complement" of Pol's Etoothpick sequence after n iterations.


0



0, 1, 4, 13, 28, 37, 64, 85, 112, 145, 172, 217, 256, 289, 364, 433, 508, 577, 628, 709, 748, 829, 904, 961, 1060, 1141, 1216, 1357, 1480, 1609, 1732, 1825, 1948, 2017, 2128, 2245, 2356, 2509, 2656, 2797, 2944, 3097, 3292, 3481, 3628, 3817, 3964, 4117, 4300, 4489, 4648, 4849, 5209, 5416, 5581, 5788, 5965, 6196, 6445, 6700
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OFFSET

0,3


COMMENTS

In the Etoothpick pattern of Omar E. Pol (see A161330 and accompanying drawings), equivalently each Etoothpick can be replaced by a rhombus (with edge or side length = 1) in an obvious way. Let r denote the area of the rhombus. The nth iteration of the pattern is bounded by a regular hexagon with edge length n, so the total area of that nth hexagonal region is equal to 3*n^2*r. Then after n iterations, a(n) = (total area in the bounded hexagonal region not occupied by rhombi)/r = (number of "missing rhombi"). The resulting pattern of the unoccupied region we call the "complement" of the Etoothpick pattern.


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KEYWORD

nonn


AUTHOR



STATUS

approved



