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 A118673 Positive solutions x to the equation x^2 + (x+71)^2 = y^2. 14
 0, 13, 160, 213, 280, 1113, 1420, 1809, 6660, 8449, 10716, 38989, 49416, 62629, 227416, 288189, 365200, 1325649, 1679860, 2128713, 7726620, 9791113, 12407220, 45034213, 57066960, 72314749, 262478800, 332610789, 421481416, 1529838729, 1938597916, 2456573889 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Consider all Pythagorean triples (x,x+71,y) ordered by increasing y; sequence gives x values. For the generic case x^2+(x+p)^2=y^2 with p=2*m^2-1 a prime number in A066436, m>=2 the associated value in A066049, the x values are given by the sequence defined by: a(n) = 6*a(n-3) -a(n-6) + 2*p with a(0)=0, a(1)=2m+1, a(2)=6m^2-10m+4, a(3)=3p, a(4)=6m^2+10m+4, a(5)=40m^2-58m+21. For the generic case x^2+(x+p)^2=y^2 with p=2*m^2-1 a prime number in A066436, m>=2, Y values are given by the sequence defined by: b(n)=6*b(n-3)-b(n-6) with b(0)=p, b(1)=2m^2+2m+1, b(2)=10m^2-14m+5, b(3)=5p, b(4)=10m^2+14m+5, b(5)=58m^2-82m+29. - Mohamed Bouhamida, Sep 09 2009 LINKS G. C. Greubel, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (1,0,6,-6,0,-1,1). FORMULA a(n) = 6*a(n-3) -a(n-6) +142 with a(0)=0, a(1)=13, a(2)=160, a(3)=213, a(4)=280, a(5)=1113. O.g.f.: x*(13+147*x+53*x^2-11*x^3-49*x^4-11*x^5)/((1-x)*(1-6*x^3+x^6)). - R. J. Mathar, Jun 10 2008 MATHEMATICA Select[Range[0, 100000], IntegerQ[Sqrt[#^2+(#+71)^2]]&] (* or *) LinearRecurrence[{1, 0, 6, -6, 0, -1, 1}, {0, 13, 160, 213, 280, 1113, 1420}, 100] (* Vladimir Joseph Stephan Orlovsky, Feb 02 2012 *) PROG (PARI) a(n)=([0, 1, 0, 0, 0, 0, 0; 0, 0, 1, 0, 0, 0, 0; 0, 0, 0, 1, 0, 0, 0; 0, 0, 0, 0, 1, 0, 0; 0, 0, 0, 0, 0, 1, 0; 0, 0, 0, 0, 0, 0, 1; 1, -1, 0, -6, 6, 0, 1]^n*[0; 13; 160; 213; 280; 1113; 1420])[1, 1] \\ Charles R Greathouse IV, Apr 22 2016 (PARI) x='x+O('x^30); concat([0], Vec(x*(13+147*x+53*x^2-11*x^3 -49*x^4 -11*x^5)/((1-x)*(1-6*x^3+x^6)))) \\ G. C. Greubel, May 07 2018 (MAGMA) m:=25; R:=PowerSeriesRing(Integers(), m); [0] cat Coefficients(R!(x*(13+147*x+53*x^2-11*x^3-49*x^4-11*x^5)/((1-x)*(1 - 6*x^3 +x^6)))); // G. C. Greubel, May 07 2018 CROSSREFS Cf. A076296 (p=7), A118120 (p=17), A118674 (p=31), A129836 (p=97), A129992 (p=127), A129993 (p=199), A129991 (p=241), A129999 (p=337), A130004 (p=449), A130005 (p=577), A130013 (p=647), A130014 (p=881), A130017 (p=967). Sequence in context: A000830 A205170 A205163 * A216300 A250417 A212785 Adjacent sequences:  A118670 A118671 A118672 * A118674 A118675 A118676 KEYWORD nonn,easy AUTHOR Mohamed Bouhamida, May 19 2006 EXTENSIONS Edited by R. J. Mathar, Jun 10 2008 STATUS approved

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Last modified May 30 05:35 EDT 2020. Contains 334712 sequences. (Running on oeis4.)