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A037521 Base-4 digits are, in order, the first n terms of the periodic sequence with initial period 2, 1, 0. 2
2, 9, 36, 146, 585, 2340, 9362, 37449, 149796, 599186, 2396745, 9586980, 38347922, 153391689, 613566756, 2454267026, 9817068105, 39268272420, 157073089682, 628292358729, 2513169434916, 10052677739666, 40210710958665 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (4,0,1,-4).

FORMULA

a(n) = floor(4^(n+1)/7). - Mircea Merca, Dec 26 2010

G.f.: x*(2+x) ) / ( (1-x)*(1-4*x)*(1+x+x^2) ).

a(n) = 4*a(n-1) + a(n-3) - 4*a(n-4).

a(n) = 4^(n+1)/7 - 1/3 - (-1)^(n mod 3)*A167380(4 + (n mod 3))/21 = 2*A033140(n) + A033140(n-1). - R. J. Mathar, Jan 08 2011

MAPLE

seq(floor(4^(n+1)/7), n=1..30); # Mircea Merca, Dec 26 2010

MATHEMATICA

Table[FromDigits[PadRight[{}, n, {2, 1, 0}], 4], {n, 30}] (* Harvey P. Dale, Jul 03 2017 *)

PROG

(MAGMA) [Floor(4^(n+1)/7) : n in [1..30]]; // Vincenzo Librandi, Jun 25 2011

CROSSREFS

Sequence in context: A077836 A003125 A055841 * A037730 A029874 A052834

Adjacent sequences:  A037518 A037519 A037520 * A037522 A037523 A037524

KEYWORD

nonn,base,easy

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified March 19 17:20 EDT 2019. Contains 321330 sequences. (Running on oeis4.)