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A031637 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 49. 0
15401, 29633, 48922, 49810, 135649, 139354, 175013, 178373, 217517, 221261, 225037, 270841, 325429, 328858, 376394, 377621, 382549, 383786, 386266, 387509, 390001, 446953, 449629, 522125, 525017, 581605, 583130, 586186, 589250, 596945, 598490 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MATHEMATICA

ct49Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=ContinuedFraction[s]; If[IntegerQ[ s], len=2, len=Length[cf[[2]]]]; OddQ[len]&&cf[[2]][[(len+1)/2]]==49]; Select[ Range[600000], ct49Q] (* Harvey P. Dale, Sep 19 2014 *)

CROSSREFS

Sequence in context: A252990 A252842 A261724 * A054838 A255148 A054839

Adjacent sequences:  A031634 A031635 A031636 * A031638 A031639 A031640

KEYWORD

nonn

AUTHOR

David W. Wilson

EXTENSIONS

Corrected and extended by Harvey P. Dale, Sep 19 2014

STATUS

approved

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Last modified June 29 05:01 EDT 2022. Contains 354910 sequences. (Running on oeis4.)