%I A081783
%S A081783 1,4,172,181307,241328833528,824652019956267685427678,
%T A081783 768422457901766762303892554138930904416139509281,
%U A081783 2110688056630901907060877896737932376507936264268382076456539236145849709148481095915090382331184
%N A081783 Continued cotangent for zeta(2)=Pi^2/6.
%F A081783 Pi^2/6=cot(sum(n>=0, n, (-1)^n*acot(a(n))); let b(0)=Pi^2/6, b(n)=(b(n-1)*floor(b(n-1))+1)/
               (b(n-1)-floor(b(n-1)) then a(n)=floor(b(n))
%o A081783 (PARI) ?bn=vector(100); b(n)=if(n<0,0,bn[n]); bn[1]=Pi^2/6; ?for(n=2,
               10,bn[n]=(b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1)))) ?a(n)=floor(b(n+1))
%Y A081783 Cf. A001620, A002666, A002667.
%Y A081783 Sequence in context: A051476 A057140 A145245 this_sequence A006433 A113254 
               A127606
%Y A081783 Adjacent sequences: A081780 A081781 A081782 this_sequence A081784 A081785 
               A081786
%K A081783 nonn
%O A081783 0,2
%A A081783 Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 10 2003