%I A046180
%S A046180 1,40755,1533776805,57722156241751,2172315626468283465,
%T A046180 81752926228785223683195,3076689623521787481625080301,
%U A046180 115788137209866023854693048367775
%N A046180 Hexagonal pentagonal numbers.
%H A046180 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               HexagonalPentagonalNumber.html">Link to a section of The World of 
               Mathematics.</a>
%F A046180 a(n) = 37634*a(n-1) - a(n-2) + 3136; g.f.: (1+3120*x+15*x^2)/((1-x)*(1-37634*x+x^2)) 
               - Warut Roonguthai (warut822(AT)yahoo.com) Jan 08 2001
%F A046180 a(n+1)=18817*a(n)+1568+1358*(192*a(n)^2+32*a(n)+1)^0.5 - Richard Choulet 
               (richardchoulet(AT)yahoo.fr), Sep 19 2007
%F A046180 a(n)=-(1/12)+(5/16)*sqrt(3)*{[18817+10864*sqrt(3)]^n-[18817-10864*sqrt(3)]^n}+(13/
               24)*[18817+10864*sqrt(3)]^n+[18817-10864*sqrt(3)]^n }, with n>=0 
               [From Paolo P. Lava (ppl(AT)spl.at), Nov 25 2008]
%Y A046180 Cf. A046178, A046179.
%Y A046180 Cf. A046178 A046179.
%Y A046180 Sequence in context: A033984 A090060 A097238 this_sequence A164648 A097479 
               A133863
%Y A046180 Adjacent sequences: A046177 A046178 A046179 this_sequence A046181 A046182 
               A046183
%K A046180 nonn,easy
%O A046180 1,2
%A A046180 Eric Weisstein (eric(AT)weisstein.com)