A031613 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 25.

1453, 7793, 13306, 13537, 19165, 20285, 28393, 35569, 37861, 46514, 47378, 47813, 57961, 58925, 60877, 83473, 84629, 85793, 86378, 88738, 100481, 101114, 101749, 104309, 104954, 105601, 114973, 116329, 123229, 131885, 133337, 134797, 136265, 139225

Offset

1,1

Links

Table of n, a(n) for n=1..34.

Mathematica

cf25Q[n_]:=Module[{s=Sqrt[n], c, len}, c=If[IntegerQ[s], {0, 0}, ContinuedFraction[ s][[2]]]; len=Length[c]; OddQ[len] && c[[Floor[ len/2]+ 1]] == 25]; Select[Range[140000], cf25Q] (* Harvey P. Dale, Nov 22 2013 *)

Crossrefs

Sequence in context: A068280 A020396 A052237 * A289822 A145529 A203393

Adjacent sequences: A031610 A031611 A031612 * A031614 A031615 A031616

Keyword

nonn

Author

David W. Wilson

Extensions

Corrected and extended by Harvey P. Dale, Nov 22 2013

Status

approved