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A167190 1+85*n+2232*n^2+15276*n^3. 3
17594, 131307, 432796, 1013717, 1965726, 3380479, 5349632, 7964841, 11317762, 15500051, 20603364, 26719357, 33939686, 42356007, 52059976, 63143249, 75697482, 89814331, 105585452, 123102501, 142457134, 163741007, 187045776 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

As mentioned in A166957, polynomials in two variables, not necessarily homogeneous, also have a property similar to that in a single variable (cf. A165806, A165808 and A165809) viz f(x+k*f(x,y), y + k*f(x,y)) is congruent to 0 (mod(f(x,y)). The quotient has two parts: a rational integer and a rational integer coefficient of sqrt(-1), when x belongs to Z(x = 5) and y is complex (sqrt(-1)). The polynomial considered is identical with that in A166957 viz x^3 + 2xy + y^2. The present sequence is only that of the rational integers and seq A167191 will consist of rational integer coefficients of sqrt(-1). Note: k belongs to N.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

FORMULA

G.f.: -x*(-17594-60931*x-13132*x^2+x^3) / (x-1)^4 . - R. J. Mathar, Sep 02 2011

a(n) = +4*a(n-1) -6*a(n-2) +4*a(n-3) -a(n-4). - R. J. Mathar, Sep 02 2011

E.g.f.: (15276*x^3 + 48060*x^2 + 17593*x + 1)*exp(x). - G. C. Greubel, Apr 09 2016

EXAMPLE

When x = 5 and y = i, f(x,y) = x^3 + 2xy + y^2 = 124 + 10i. The quotient of f(x + f(x,y), y + f(x,y))/(124 + 10i) is 17594 + 2664i.

MATHEMATICA

CoefficientList[Series[(17594+60931*x+13132*x^2-x^3)/(x-1)^4, {x, 0, 40}], x] (* Vincenzo Librandi, Jul 02 2012 *)

PROG

(MAGMA)  I:=[17594, 131307, 432796, 1013717]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..40]]; // Vincenzo Librandi, Jul 02 2012

CROSSREFS

Cf. A165806, A165808, A165809, A166957.

Sequence in context: A203963 A253403 A213107 * A203353 A273035 A036377

Adjacent sequences:  A167187 A167188 A167189 * A167191 A167192 A167193

KEYWORD

nonn,easy

AUTHOR

A.K. Devaraj, Oct 30 2009

EXTENSIONS

Extended beyond a(6) by R. J. Mathar, Nov 17 2009

STATUS

approved

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Last modified July 22 05:47 EDT 2019. Contains 325213 sequences. (Running on oeis4.)