Search: id:A074061
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%I A074061
%S A074061 1,4,6,39,59,386,584,3821,5781,37824,57226,374419,566479,3706366,
%T A074061 5607564,36689241,55509161,363186044,549484046,3595171199,5439331299,
%U A074061 35588525946,53843828944,352290088261,532998958141,3487312356664
%N A074061 Positive integers n such that 24*n^2-23 is a square.
%H A074061 <a href="Sindx_Tu.html#2wis">Index entries for two-way infinite sequences</
               a>
%H A074061 K. S. Brown, <a href="http://www.mathpages.com/home/kmath275.htm">Numbers 
               Expressible as (a^2-1)(b^2-1)</a>
%F A074061 a(2n-1) = round((1/2)*(1-(1/2)/sqrt(6))*(sqrt(2)+sqrt(3))^(2n)); a(2n)=round(c*(sqrt(2)+sqrt(3))^(2n+1)) 
               with c =0.191357750597... - Benoit Cloitre (benoit7848c(AT)orange.fr), 
               Aug 22 2002
%F A074061 G.f.: (1-x)(1+5x+x^2)/(1-10x^2+x^4). a(n)=10a(n-2)-a(n-4)=a(-1-n).
%o A074061 (PARI) a(n)=if(n<0,a(-1-n),polcoeff((1-x)*(1+5*x+x^2)/(1-10*x^2+x^4)+x*O(x^n),
               n))
%Y A074061 Sequence in context: A092765 A056315 A103234 this_sequence A125081 A023644 
               A145387
%Y A074061 Adjacent sequences: A074058 A074059 A074060 this_sequence A074062 A074063 
               A074064
%K A074061 nonn
%O A074061 0,2
%A A074061 Michael Somos, Aug 19, 2002

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