%I
%S 3,9,21,57,129,345,777,2073,4665,12441,27993,74649,167961,447897,
%T 1007769,2687385,6046617,16124313,36279705,96745881,217678233,
%U 580475289,1306069401,3482851737,7836416409,20897110425,47018498457
%N a(n) = Sum{T(i,j)}, 0<=j<=i, 0<=i<=2n, T given by A026536.
%C The even terms are the number of holes of SierpiĆski trianglelike fractals. The odd terms are the total number of holes and triangles.  _Kival Ngaokrajang_, Mar 30 2014
%C All terms are divisible by 3 (see g.f.).  _Joerg Arndt_, Dec 20 2014
%H Kival Ngaokrajang, <a href="/A026551/a026551.pdf">Illustration of initial terms</a>
%F G.f.: 3*(1+2*x2*x^2)/((1x)*(16*x^2)).  _Ralf Stephan_, Feb 03 2004
%o (PARI) Vec( 3*(1+2*x2*x^2)/((1x)*(16*x^2))+O(x^33)); \\ _Joerg Arndt_, Dec 20 2014
%Y Cf. A026534, A026565.
%K nonn,easy
%O 0,1
%A _Clark Kimberling_
