[seqfan] Reproducing A064690 (sign changes of a rational fraction iteration)

Sean A. Irvine sairvin at gmail.com
Sun Jul 23 05:25:34 CEST 2023

I'm finding reproducing A064690 surprisingly difficult despite its simple


It is my suspicion that the later terms were computed with insufficient

Computing it exactly using rational arithmetic seems too slow to reach the
values listed.  Instead, I computed (using constructible real arithmetic --
which in theory should also be correct): 2, 4, 7, 11, 13, 22, 23, 332, 560,
565, 566, 568, 616, 618, 1161, 1163, 1167 but this does not match existing
terms beyond 568.

Could someone please make an attempt to verify (or come up with a better
way to compute this sequence) ?


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