%I A021913
%S A021913 0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,
%T A021913 0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,
%U A021913 1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1,0,0,1
%N A021913 Decimal expansion of 1/909.
%C A021913 Except for first term, binary expansion of the decimal number 1/10 = 
               0,000110011001100110011....in base 2 - Benoit Cloitre (benoit7848c(AT)orange.fr), 
               May 18 2002
%C A021913 Content of #2 binary placeholder when n is converted from decimal to 
               binary. a(n) = Mod(n*(n-1)/2,2). Example: a(7) = 1 since 7 in binary 
               is 1 -1- 1 and (7*6/2) mod 2 = 1 - Anne M. Donovan (anned3005(AT)aol.com) 
               Sep 15 2003
%C A021913 Expansion in any base b of 1/((b-1)(b^2+1)) = 1/(b^3-b^2+b-1). E.g., 
               1/5 in base 2, 1/20 in base 3, 1/51 in base 4, etc. - Franklin T. 
               Adams-Watters (FrankTAW(AT)Netscape.net), Nov 07 2006
%H A021913 <a href="Sindx_Ch.html#Cheby">Index entries for sequences related to 
               Chebyshev polynomials.</a>
%F A021913 G.f. : (x^2+x^3)/(1-x^4); a(n)=1/2-cos(pi*n/2)/2-sin(pi*n/2)/2; a(n)=a(n-1)-a(n-2)+a(n-3). 
               - Paul Barry (pbarry(AT)wit.ie), Aug 30 2004
%F A021913 a(n+2)=sum(b(k), k=0..n), n>=0, with b(k):=A056594(k) (partial sums of 
               S(n, x) Chebyshev polynomials at x=0).
%F A021913 a(n)=-a(n-2)+1, n>=2, a(0)=0=a(1).
%F A021913 G.f.: x^2/((1-x)*(1+x^2))=x^2/(1-x+x^2-x^3).
%F A021913 a(n)=(1/12)*{4*(n mod 4)+[(n+1) mod 4]-2*[(n+2) mod 4]+[(n+3) mod 4]}, 
               with n>=0 - Paolo P. Lava (ppl(AT)spl.at), Oct 23 2007
%F A021913 Contribution from Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Dec 
               05 2008: (Start)
%F A021913 a(n)=1/2-sin((2n+1)pi/4)/sqrt(2)
%F A021913 a(n)=1/2-cos((2n-1)pi/4)/sqrt(2) (End)
%Y A021913 Cf. A062158.
%Y A021913 Sequence in context: A074290 A091225 A132380 this_sequence A156660 A155899 
               A117814
%Y A021913 Adjacent sequences: A021910 A021911 A021912 this_sequence A021914 A021915 
               A021916
%K A021913 nonn,cons
%O A021913 0,1
%A A021913 N. J. A. Sloane (njas(AT)research.att.com).
%E A021913 Chebyshev comment from W. Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), 
               Sep 10 2004