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A020440 Period of continued fraction for sqrt(n) contains exactly four 1's. 1
13, 21, 31, 57, 61, 67, 73, 74, 92, 106, 108, 109, 111, 112, 116, 129, 137, 158, 161, 162, 183, 185, 193, 204, 207, 236, 237, 243, 246, 251, 261, 262, 265, 273, 274, 275, 282, 297, 298, 308, 314, 317, 329, 332, 341, 346, 351, 355, 364, 375, 381, 383, 384, 388, 406, 412 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..56.

MATHEMATICA

Select[ Range@ 1900, !IntegerQ[ Sqrt@ #] && Count[ ContinuedFraction[ Sqrt@ #][[2]], 1] == 4 &] (* Robert G. Wilson v, Jul 03 2011 *)

CROSSREFS

Sequence in context: A331116 A050711 A282844 * A164458 A164452 A164444

Adjacent sequences:  A020437 A020438 A020439 * A020441 A020442 A020443

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified January 16 18:07 EST 2022. Contains 350376 sequences. (Running on oeis4.)