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A111216
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a(n) = 31*a(n-1)-a(n-2).
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3
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1, 30, 929, 28769, 890910, 27589441, 854381761, 26458245150, 819351217889, 25373429509409, 785756963573790, 24333092441278081, 753540108716046721, 23335410277756170270, 722644178501725231649, 22378634123275726010849, 693015013643045781104670
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OFFSET
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0,2
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COMMENTS
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Take 31 numbers consisting of 29 ones together with any two successive terms from this sequence. This set has the property that the sum of their squares is 31 times their product. (Guy)
Positive values of x (or y) satisfying x^2 - 31xy + y^2 + 29 = 0. - Colin Barker, Feb 24 2014
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LINKS
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FORMULA
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MATHEMATICA
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CoefficientList[Series[(1 - x)/(1 - 31 x + x^2), {x, 0, 40}], x] (* Vincenzo Librandi, Feb 26 2014 *)
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PROG
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(PARI) Vec((1-x)/(1-31*x+x^2) + O(x^100)) \\ Colin Barker, Feb 24 2014
(Magma) I:=[1, 30]; [n le 2 select I[n] else 31*Self(n-1)-Self(n-2): n in [1..20]]; // Vincenzo Librandi, Feb 26 2014
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CROSSREFS
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Cf. similar sequences listed in A238379.
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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