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A067874 Positive integers x satisfying x^2 - D*y^2 = 1 for a unique integer D. 4
2, 4, 6, 12, 14, 16, 18, 20, 22, 30, 32, 34, 36, 38, 40, 42, 52, 54, 56, 58, 60, 66, 68, 70, 72, 78, 84, 86, 88, 90, 92, 94, 96, 102, 104, 106, 108, 110, 112, 114, 128, 130, 132, 138, 140, 142, 144, 150, 156, 158, 160, 162, 164, 166, 178, 180, 182, 184, 186, 192, 194, 196, 198 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

D is unique iff x^2 - 1 is squarefree, in which case it follows with necessity that D=x^2-1 and y=1.

All terms are even and include A014574 as a subsequence.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[200], SquareFreeQ[#^2-1]&] [From Vladimir Joseph Stephan Orlovsky, Oct 26 2009]

CROSSREFS

Sequence in context: A137394 A062856 A056371 * A015733 A023187 A061012

Adjacent sequences:  A067871 A067872 A067873 * A067875 A067876 A067877

KEYWORD

nice,nonn

AUTHOR

Lekraj Beedassy, Feb 25 2002

EXTENSIONS

Corrected and extended by Max Alekseyev, Apr 26 2009

Further edited by Max Alekseyev, Apr 28 2009

STATUS

approved

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Last modified May 24 08:47 EDT 2013. Contains 225617 sequences.