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A031638 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 50. 0
626, 15901, 31378, 51157, 52522, 77405, 107753, 109069, 141601, 142354, 143866, 146149, 182618, 183473, 185189, 226937, 230761, 336929, 340418, 392501, 393754, 396266, 398786, 400049, 402581, 406394, 465853, 474073, 536665, 542537, 545485 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

cf50Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1, 1}, ContinuedFraction[ s][[2]]]; len=Length[cf]; OddQ[len]&&cf[[(len+1)/2]] == 50]; Select[Range[550000], cf50Q] (* Harvey P. Dale, May 13 2019 *)

CROSSREFS

Sequence in context: A345766 A158383 A031728 * A098262 A031523 A345523

Adjacent sequences:  A031635 A031636 A031637 * A031639 A031640 A031641

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected by Harvey P. Dale, May 13 2019

STATUS

approved

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Last modified June 25 03:00 EDT 2022. Contains 354835 sequences. (Running on oeis4.)