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a(n) is the total number of pentagrams in a variant of pentagram fractal after n iterations.
7

%I #30 Aug 26 2024 20:14:46

%S 1,6,21,56,131,281,556,1046,1896,3346,5796,9916,16806,28316,47506,

%T 79476,132706

%N a(n) is the total number of pentagrams in a variant of pentagram fractal after n iterations.

%C Inspired by A255870. But at the higher iterations, the perimeter is an irregular polygon instead of a pentagon. The construction rule is sides to vertices expansion. See illustration in the links.

%H <a href="/A256571/b256571.txt">Table of n, a(n) for n = 1..17</a>

%H Kival Ngaokrajang, <a href="/A256571/a256571.pdf">Illustration of initial terms</a>

%Y Cf. A255870, A256429, A256569.

%K nonn,more

%O 1,2

%A _Kival Ngaokrajang_, Apr 02 2015

%E a(9) corrected and a(10)-a(15) added by _Udo Vieth_, Jan 16 2023

%E a(16)-a(17) added by _Udo Vieth_, Aug 19 2024