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a(n) = n(n+1)/2 - A169780(n).
3

%I #6 Nov 25 2018 13:50:32

%S 0,0,0,1,1,4,6,7,7,14,20,25,27,30,36,37,37,52,66,79,89,100,112,117,

%T 115,122,140,153,157,158,168,167,167,198,228,257,283,310,338,359,373,

%U 396,428,453,467,474,486,491,481,496,538,575,603,628,654,665,653,650,680,707,711

%N a(n) = n(n+1)/2 - A169780(n).

%C If n is a power of 2, this is the number of OFF cells after n stages in a 60-degree wedge of the hexagonal CA (see A170905, A169780, A151723, A169789).

%H N. J. A. Sloane, <a href="/A169788/b169788.txt">Table of n, a(n) for n = 0..1025</a>

%Y Cf. A170905, A169780, A151723, A169789.

%K nonn

%O 0,6

%A _N. J. A. Sloane_, May 13 2010