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 A101463 G.f.: (x^3+x^2+2*x+1)/(x^4+5*x^2+1). 0
 1, 2, -4, -9, 19, 43, -91, -206, 436, 987, -2089, -4729, 10009, 22658, -47956, -108561, 229771, 520147, -1100899, -2492174, 5274724, 11940723, -25272721, -57211441, 121088881, 274116482, -580171684, -1313370969, 2779769539, 6292738363, -13318676011 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A floretion-generated sequence relating to Pythagoras' theorem generalized. REFERENCES F. A. Haight, On a generalization of Pythagoras' theorem, pp. 73-77 of J. C. Butcher, editor, A Spectrum of Mathematics. Auckland University Press, 1971. LINKS James A. Sellers, Domino Tilings and Products of Fibonacci and Pell Numbers, Journal of Integer Sequences, Vol. 5 (2002), Article 02.1.2 Index entries for linear recurrences with constant coefficients, signature (0,-5,0,-1) FORMULA Let b(1)=1, b(2)=2, b(3)=4 and b(n)=(b(n-1)*b(n-2)+(3+(-1)^n)/2)/b(n-3) then b(n)=abs(a(n)) - Benoit Cloitre, Mar 03 2007 a(n)=-5*a(n-2)-a(n-4), n>3. [From Harvey P. Dale, Apr 15 2012] G.f.: ( 1+2*x+x^2+x^3 ) / ( 1+5*x^2+x^4 ). - R. J. Mathar, Jun 18 2014 a(n) = -3a(n-1)+2a(n-2) if n even. a(n) = (5*a(n-1)+a(n-2))/2 if n odd. - R. J. Mathar, Jun 18 2014 MATHEMATICA CoefficientList[Series[(x^3+x^2+2x+1)/(x^4+5x^2+1), {x, 0, 30}], x] (* or *) LinearRecurrence[{0, -5, 0, -1}, {1, 2, -4, -9}, 31] (* Harvey P. Dale, Apr 15 2012 *) PROG Floretion Algebra Multiplication Program. FAMP code: em[J* ]sigcycseq[ + .75'i + .5'k + .25i' + .5j' + .5k' - .25'ii' + .25'jj' - .25'kk' - .75'jk' + .5'ki' - .25'kj' + .25e] CROSSREFS Elements of even index in the sequence gives A004253. Elements of odd index in the sequence gives A002310. Cf. A004253, A002310. Sequence in context: A193021 A112569 A289845 * A206301 A026776 A117160 Adjacent sequences:  A101460 A101461 A101462 * A101464 A101465 A101466 KEYWORD easy,sign AUTHOR Creighton Dement, Jan 20 2005 STATUS approved

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