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 A081796 Continued cotangent for sin(Pi/3)=sqrt(3)/2. 0
 0, 1, 13, 196, 257087, 249639161983, 553029809670900697241813, 575598315149214535162520163688459972096324096213, 680813056961507163626080261194823226597566577785481001106845521689287461487322891517719568410606 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 433-434. D. H. Lehmer, A cotangent analogue of continued fractions, Duke Math. J., 4 (1935), 323-340. LINKS Steven R. Finch, Lehmer's Constant [broken link] Steven R. Finch, Lehmer's Constant [From the Wayback machine] FORMULA sqrt(3)/2=cot(sum(n>=0, n, (-1)^n*acot(a(n))); let b(0)=sqrt(3)/2, b(n)=(b(n-1)*floor(b(n-1))+1)/(b(n-1)-floor(b(n-1)) then a(n)=floor(b(n)) PROG (PARI) ?bn=vector(100); b(n)=if(n<0, 0, bn[n]); bn[1]=sqrt(3)/2; ?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)) CROSSREFS Cf. A002065, A002666, A002667, A002668. Sequence in context: A015690 A027773 A099271 * A140536 A289734 A130549 Adjacent sequences:  A081793 A081794 A081795 * A081797 A081798 A081799 KEYWORD nonn AUTHOR Benoit Cloitre, Apr 10 2003 STATUS approved

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Last modified January 27 23:50 EST 2020. Contains 331301 sequences. (Running on oeis4.)