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Search: id:A074061
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| A074061 |
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Positive integers n such that 24*n^2-23 is a square. |
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+0
1
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| 1, 4, 6, 39, 59, 386, 584, 3821, 5781, 37824, 57226, 374419, 566479, 3706366, 5607564, 36689241, 55509161, 363186044, 549484046, 3595171199, 5439331299, 35588525946, 53843828944, 352290088261, 532998958141, 3487312356664
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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K. S. Brown, Numbers Expressible as (a^2-1)(b^2-1)
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FORMULA
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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
G.f.: (1-x)(1+5x+x^2)/(1-10x^2+x^4). a(n)=10a(n-2)-a(n-4)=a(-1-n).
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PROGRAM
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(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))
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CROSSREFS
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Sequence in context: A092765 A056315 A103234 this_sequence A125081 A023644 A034923
Adjacent sequences: A074058 A074059 A074060 this_sequence A074062 A074063 A074064
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KEYWORD
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nonn
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AUTHOR
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Michael Somos, Aug 19, 2002
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