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A158675
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a(n)=31*(31*n^2+1).
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1
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31, 992, 3875, 8680, 15407, 24056, 34627, 47120, 61535, 77872, 96131, 116312, 138415, 162440, 188387, 216256, 246047, 277760, 311395, 346952, 384431, 423832, 465155, 508400, 553567, 600656, 649667, 700600, 753455, 808232, 864931, 923552, 984095
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| The identity (62*n^2+1)^2 - (961*n^2+31) * (2*n)^2 = 1 can be written as
the Pell equation (A158676(n))^2 - a(n) * (A005843(n))^2 = 1.
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LINKS
| Vincenzo Librandi, X^2-AY^2=1
Edward Everett Withford, Pell Equation
Wolfram MathWorld, Pell Equation
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FORMULA
| a(n)= 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: -31*(1+29*x+32*x^2)/(x-1)^3.
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CROSSREFS
| Cf. A005843, A158676
Sequence in context: A042862 A159674 A138958 * A154808 A138861 A015257
Adjacent sequences: A158672 A158673 A158674 * A158676 A158677 A158678
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 24 2009
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EXTENSIONS
| Comment rewritten, a(0) added and formula replaced by R. J. Mathar, (mathar(AT)strw.leidenuniv.nl), Oct 22 2009
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