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A031623
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 35.
0
15178, 25681, 38537, 52153, 53069, 53993, 70981, 72586, 90289, 91493, 115961, 137341, 140317, 164554, 166993, 168629, 170273, 171098, 192469, 193346, 195989, 196874, 197761, 201329, 229213, 258905, 260941, 262985, 265037, 267097, 271241
OFFSET
1,1
MATHEMATICA
ct35Q[n_]:=Module[{s=Sqrt[n], cf, len, ctr}, If[IntegerQ[s], cf={1, 1}, cf= ContinuedFraction[ s][[2]]]; len=Length[cf]; ctr=Floor[len/2]; OddQ[len] && Take[cf, {ctr, ctr+1}]=={35, 35}]; Select[Range[280000], ct35Q] (* Harvey P. Dale, Apr 16 2013 *)
CROSSREFS
Subsequence of A003814.
Sequence in context: A004975 A157436 A196495 * A105924 A259395 A233924
KEYWORD
nonn
EXTENSIONS
Corrected by Harvey P. Dale, Apr 16 2013
STATUS
approved