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A055989 a(n) is its own 4th difference. 4
1, 3, 10, 36, 131, 476, 1728, 6272, 22765, 82629, 299915, 1088589, 3951206, 14341527, 52054840, 188941273, 685792227, 2489191330, 9034913540, 32793647355, 119029728628, 432037221840, 1568147413312, 5691839002677 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (5,-6,4,-1).

FORMULA

a(n) = 5*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) = a(n-1) + A055988(n) = A055990(n) - A055990(n-1) = A055991(n) - 2*A055991(n-1) + A055991(n-2).

G.f.: x*(1-x)^2/(1 - 5*x + 6*x^2 - 4*x^3 + x^4). - Colin Barker Apr 04 2012

MATHEMATICA

CoefficientList[Series[(1-x)^2/(1-5*x+6*x^2-4*x^3+x^4), {x, 0, 40}], x] (* Vincenzo Librandi, Apr 05 2012 *)

LinearRecurrence[{5, -6, 4, -1}, {1, 3, 10, 36}, 30] (* Harvey P. Dale, Jan 10 2014 *)

PROG

(MAGMA) I:=[1, 3, 10, 36]; [n le 4 select I[n] else 5*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Apr 05 2012

CROSSREFS

Cf. A055988, A055990, A055991 for the other differences of a(n). See A000079, A001906, A052529 for examples of sequences which are respectively their own first, second and third differences.

Sequence in context: A047122 A047107 A149040 * A102871 A277287 A119374

Adjacent sequences:  A055986 A055987 A055988 * A055990 A055991 A055992

KEYWORD

nonn,easy

AUTHOR

Henry Bottomley, Jun 02 2000

EXTENSIONS

More terms from James A. Sellers, Jun 05 2000

STATUS

approved

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Last modified December 11 04:29 EST 2018. Contains 318049 sequences. (Running on oeis4.)