A081466 Consider the mapping f(a/b) = (a^2+b^2)/(a^2-b^2) from rationals to rationals. Starting with 2/1 (a=2, b=1) and applying the mapping to each new (reduced) rational number gives 2/1, 5/3, 17/8, 353/225, ... Sequence gives values of the denominators.

1, 3, 8, 225, 36992, 6308330625, 21009822254496776192, 3255818067933293622186199316985612890625, 3264008661830516310447364816658205121507617681188862393654856638929469798612992

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Prog

(PARI) {r=2; for(n=1, 9, a=numerator(r); b=denominator(r); print1(b, ", "); r=(a^2+b^2)/(a^2-b^2))}

Crossrefs

Cf. A000058, A081461, A081462, A081465.

Sequence in context: A132563 A065061 A007159 * A092592 A162185 A297527

Adjacent sequences: A081463 A081464 A081465 * A081467 A081468 A081469

Keyword

nonn

Author

Amarnath Murthy, Mar 22 2003

Extensions

Edited and extended by Klaus Brockhaus, Mar 24 2003

Status

approved