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.

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

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