A031576 Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 78.

6086, 6098, 6102, 6114, 6134, 6158, 6166, 6182, 6194, 6198, 6226, 6238, 6246, 6278, 6294, 6302, 6306, 6326, 6334, 6338, 6358, 6374, 6382, 6398, 13692, 13701, 13737, 13749, 13758, 13764, 13773, 13791, 13809, 13863, 13881, 13917, 13929, 13953, 13989

Offset

1,1

Links

Table of n, a(n) for n=1..39.

Mathematica

cf78Q[n_]:=Module[{s=Sqrt[n], cf, len}, cf=If[IntegerQ[s], {1}, ContinuedFraction[s][[2]]]; len = Length[ cf]; EvenQ[len]&&cf[[len/2]]==78]; Select[Range[14000], cf78Q] (* Harvey P. Dale, Jan 31 2024 *)

Crossrefs

Sequence in context: A084804 A274360 A025515 * A204966 A252329 A156200

Adjacent sequences: A031573 A031574 A031575 * A031577 A031578 A031579

Keyword

nonn

Author

David W. Wilson

Status

approved