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%I #11 May 02 2020 05:29:19
%S 1,12,48,147,291,519,879,1383,2079,3039,4359,5991,7983,10515,13731,
%T 17571,22131,27543,33951,41271,49599,59355,70779,83499,97611,113763,
%U 132243,152619,175035,199707,226827,256443,288747,324603,364395,407139,452979,503319
%N Number of triangular regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition),
%C See A328526 for images of the triangular frame.
%H Lars Blomberg, <a href="/A333032/b333032.txt">Table of n, a(n) for n = 1..65</a>
%Y Cf. A328526 (regions), A333030 (edges), A333031 (vertices), A333033 (4-gons), A331776 (square frame), A274586 (filled triangle).
%K nonn
%O 1,2
%A _Scott R. Shannon_ and _N. J. A. Sloane_, Mar 05 2020
%E a(12) and beyond from _Lars Blomberg_, May 01 2020