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a(1) = 1, a(2) = 8; for n > 2: a(n) = a(n-1)*(3*a(n-1)-2).
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%I #19 Sep 09 2023 11:34:36

%S 1,8,176,92576,25710762176,1983129874961075240576,

%T 11798412302889389755255045998938726679954176,

%U 417607598606915139792416465578985202696175989567316713156694229302007260054247019608576

%N a(1) = 1, a(2) = 8; for n > 2: a(n) = a(n-1)*(3*a(n-1)-2).

%C n*(3n-2) is the n-th octagonal number (A000567).

%F a(n) = (A003487(n-1)+1)/3 for n >= 2. - _Ondrej Kutal_, Sep 08 2023

%t Join[{1}, NestList[ #*(3*# - 2) &, 8, 7]]

%Y Cf. A000567, A003487.

%K nonn

%O 1,2

%A _Jonathan Vos Post_, Nov 15 2004

%E Edited by _Stefan Steinerberger_, Jul 25 2007