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A189741 a(1)=4,  a(2)=2, a(n) = 4*a(n-1) + 2*a(n-2). 14
4, 2, 16, 68, 304, 1352, 6016, 26768, 119104, 529952, 2358016, 10491968, 46683904, 207719552, 924246016, 4112423168, 18298184704, 81417585152, 362266710016, 1611902010368, 7172141461504, 31912369866752, 141993762390016, 631799789293568, 2811186681954304 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..100

Index entries for linear recurrences with constant coefficients, signature (4, 2).

FORMULA

a(n) = 2*((2+sqrt(6))^(n-1)+(2-sqrt(6))^(n-1))+1/2*sqrt(6)*((2-sqrt(6))^(n-1)-(2+sqrt(6))^(n-1)). - Paolo P. Lava, May 24 2011

G.f.: 2*x*(2-7*x)/(1-4*x-2*x^2). - Bruno Berselli, May 24 2011

MATHEMATICA

LinearRecurrence[{4, 2}, {4, 2}, 40]

PROG

(Maxima) a[1]:4$ a[2]:2$ a[n]:=4*a[n-1]+2*a[n-2]$ makelist(a[n], n, 1, 25);  \\ Bruno Berselli, May 24 2011

CROSSREFS

Cf. A000045, A000079, A105476, A159612, A080040, A135522, A103435, A189732, A189734, A189735, A189736, A189737, A189738, A189739, A189742, A189743, A189744, A189745, A189746, A189747, A189748, A189749.

Sequence in context: A182872 A137393 A122749 * A303142 A285595 A255566

Adjacent sequences:  A189738 A189739 A189740 * A189742 A189743 A189744

KEYWORD

nonn

AUTHOR

Harvey P. Dale, Apr 26 2011

STATUS

approved

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Last modified September 15 04:28 EDT 2019. Contains 327062 sequences. (Running on oeis4.)