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A156774 6561n^2 - 3564n + 485. 3
485, 3482, 19601, 48842, 91205, 146690, 215297, 297026, 391877, 499850, 620945, 755162, 902501, 1062962, 1236545, 1423250, 1623077, 1836026, 2062097, 2301290, 2553605, 2819042, 3097601, 3389282, 3694085, 4012010, 4343057, 4687226 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The identity (6561*n^2-3564*n+485)^2-(81*n^2-44*n+6)*(729*n-198)^2=1 can be written as a(n)^2-A156676(n)* A156772(n)^2=1 for n>0.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).

G.f.: (-485-2027*x-10610*x^2)/(x-1)^3.

MATHEMATICA

LinearRecurrence[{3, -3, 1}, {485, 3482, 19601}, 40]

PROG

(MAGMA) I:=[485, 3482, 19601]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]];

(PARI) a(n)= 6561*n^2-3564*n+485 \\ Charles R Greathouse IV, Dec 23 2011

CROSSREFS

Cf. A156676, A156772.

Sequence in context: A160090 A158326 A031722 * A031632 A097767 A031520

Adjacent sequences:  A156771 A156772 A156773 * A156775 A156776 A156777

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Feb 15 2009

EXTENSIONS

Edited by Charles R Greathouse IV, Jul 25 2010

STATUS

approved

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Last modified June 6 18:59 EDT 2020. Contains 334832 sequences. (Running on oeis4.)