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%I
%S 1,12,3972,156624027132,9605393649115032262909140007773492,
%T 2215570185245038872814956021479696635481690776469126111743280383568619886232750745465064720338596867052
%N Iterated icosahedral numbers: a(0)=1, a(1) = 12, a(n+1)=A006564(a(n)).
%C This starts at a(1)=A006564(2)=12. An alternative, for example: if a(1) were set to A006564(3) = 48,
%C then a(2) = A006564(48) = 270768, a(3) = A006564(270768) = 49628416238058288;
%C a(4) = A006564(49628416238058288) = 305584454132546884153602392143848716431702444690608 etc.
%D Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, p. 50, 1996.
%D J. V. Post, "Iterated Triangular Numbers", preprint.
%H H. K. Kim, <a href="http://dx.doi.org/10.1090/S0002-9939-02-06710-2">On Regular Polytope Numbers</a>, Proc. Amer. Math. Soc. 131 (2003), 65-75. <a href="http://www.ams.org/mathscinet-getitem?mr=1929024">MR 1929024</a>
%H J. V. Post, <a href="http://www.magicdragon.com/poly.html">Table of Polytope Numbers, Sorted, Through 1,000,000</a>.
%e a(2) = A006564(a(1)) = A006564(12) = 12*(5*12^2 - 5*12 + 2)/2 = 3972.
%Y Cf. A007501, A006564.
%K easy,nonn
%O 0,2
%A _Jonathan Vos Post_, Nov 15 2004
%E Definition and comments condensed by _R. J. Mathar_, Sep 09 2009
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