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 A020640 Increasing periods of continued fraction for sqrt(n) (period of continued fraction for sqrt(A013645(n))). 2
 1, 2, 4, 5, 6, 8, 10, 12, 16, 18, 20, 22, 26, 34, 37, 40, 42, 44, 48, 52, 54, 60, 62, 64, 70, 76, 79, 88, 94, 96, 102, 104, 108, 114, 118, 122, 130, 136, 152, 156, 158, 170, 172, 174, 194, 196, 202, 207, 210, 217, 228, 234, 238, 239, 248, 262, 268, 280, 281 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Patrick McKinley, Table of n, a(n) for n=1..512 MATHEMATICA per[n_] := ContinuedFraction[Sqrt[n]][[2]] // Length; record = 0; t = Reap[For[n = 1, n < 2*10^4, n++, If[ !IntegerQ[Sqrt[n]], p = per[n]; If[p > record, record = p; Print[{n, p}]; Sow[{n, p}]]]]][[2, 1]]; A020640 = t[[All, 2]] (* Jean-François Alcover, Dec 27 2012 *) CROSSREFS Sequence in context: A077255 A262439 A091413 * A068383 A276603 A175416 Adjacent sequences:  A020637 A020638 A020639 * A020641 A020642 A020643 KEYWORD nonn,nice AUTHOR STATUS approved

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