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a(n) = floor(4^n/(2 + sqrt(2))^n).
11

%I #19 Jul 05 2017 20:11:37

%S 1,1,1,1,1,2,2,3,3,4,4,5,6,7,9,10,12,14,17,20,23,27,32,38,44,52,61,71,

%T 84,98,115,135,158,185,217,255,299,350,410,480,563,659,773,905,1061,

%U 1243,1456,1706,1999,2342,2744,3215,3767,4413,5170,6057,7097,8314

%N a(n) = floor(4^n/(2 + sqrt(2))^n).

%C a(n) is the perimeter (rounded down) of octaflake after n iterations, let a(0) = 1. The total number of sides is 8*A000302(n). The total number of holes is A084990(A000225(n)). sqrt(2) = A002193.

%H G. C. Greubel, <a href="/A240572/b240572.txt">Table of n, a(n) for n = 0..1000</a>

%H Kival Ngaokrajang, <a href="/A240572/a240572.pdf">Illustration of octaflake for n = 0..3</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/N-flake">n-flake</a>

%p A240572:=n->floor(4^n/(2 + sqrt(2))^n); seq(A240572(n), n=0..50); # _Wesley Ivan Hurt_, Apr 12 2014

%t Table[Floor[4^n/(2 + Sqrt[2])^n], {n, 0, 50}] (* _Wesley Ivan Hurt_, Apr 12 2014 *)

%o (PARI) {a(n)=floor(4^n/(2 + sqrt(2))^n)}

%o for (n=0, 100, print1(a(n), ", "))

%Y Cf. A000302, A084990, A000225, A002193. A240523 (pentaflake), A240671 (heptaflake), A240733 (nonaflake), A240734 (decaflake), A230735 (dodecaflake).

%K nonn,easy

%O 0,6

%A _Kival Ngaokrajang_, Apr 08 2014