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 A129207 Second sequence in solution to congruent number 5 problem. 4
 1, 1, -49, -4799, 4728001, 18618840001, -767067390499249, -54213419267800732799, 250137278774864229623059201, -1127677799839642474480271473583999, -195577262542844878506138849501555847171249 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Let W(n)=A129206(n), X(n)=A129207(n), Y(n)=A129208(n), Z(n)=A129209(n). These four sequences correspond to the four Jacobi theta functions or Weierstrass sigma functions. REFERENCES J. V. Uspensky and M. A. Heaslet, Elementary Number Theory, McGraw-Hill, 1939. See p. 427. LINKS Seiichi Manyama, Table of n, a(n) for n = 0..49 FORMULA Right triangle with sides |10*Y(n)*W(n) / (X(n)*Z(n))|, |X(n)*Z(n) / (Y(n)*W(n))|, |2*Y(2*n) / W(2*n)| has area 5. X(2*n) = X(n)^4 - 50 * W(n)^4. a(n+2) * a(n-2) = 144 * a(n+1) * a(n-1) + 2257 * a(n)^2. a(-n) = a(n). PROG (PARI) {a(n) = n=abs(n); if( n<1, 1, if( n<4, [1, -49, -4799][n], (144 * a(n-1) * a(n-3) + 2257 * a(n-2)^2 ) / a(n-4) ))}; CROSSREFS Sequence in context: A218317 A283229 A109344 * A243944 A144928 A053772 Adjacent sequences:  A129204 A129205 A129206 * A129208 A129209 A129210 KEYWORD sign AUTHOR Michael Somos, Apr 03 2007 STATUS approved

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Last modified July 4 17:20 EDT 2022. Contains 355083 sequences. (Running on oeis4.)