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A021408 Decimal expansion of 1/404. 1
0, 0, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2, 4, 7, 5, 2 (list; constant; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

After the first two terms, a(n) is periodic with period 4: repeat [2, 4, 7, 5]. - Wesley Ivan Hurt, Jul 10 2016

LINKS

Table of n, a(n) for n=0..98.

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

FORMULA

a(n) = (1/4){[(n+1) mod 4]+6*[(n+2) mod 4]+5*[(n+3) mod 4]}-7*[C(2*n,n) mod 2]-5*{C[(n+1)^2,n+3] mod 2}. - Paolo P. Lava, Feb 25 2008

From Wesley Ivan Hurt, Jul 10 2016: (Start)

G.f.: x^2*(2+2*x+5*x^2)/(1-x+x^2-x^3).

a(n) = a(n-1) - a(n-2) + a(n-3) for n>4, a(n) = a(n-4) for n>5.

a(n) = (9 + 5*cos(n*Pi/2) + sin(n*Pi/2))/2 for n>1. (End)

EXAMPLE

0.0024752475247524752475247...

MAPLE

Digits:=100: evalf(1/404); # Wesley Ivan Hurt, Jul 10 2016

MATHEMATICA

Join[{0, 0}, RealDigits[1/404, 10, 120][[1]]] (* or *) PadRight[{0, 0}, 120, {7, 5, 2, 4}] (* Harvey P. Dale, May 18 2012 *)

CoefficientList[Series[x^2*(2 + 2*x + 5*x^2)/(1 - x + x^2 - x^3), {x, 0, 30}], x] (* Wesley Ivan Hurt, Jul 10 2016 *)

PROG

(MAGMA) [0, 0] cat &cat [[2, 4, 7, 5]^^30]; // Wesley Ivan Hurt, Jul 10 2016

CROSSREFS

Sequence in context: A167280 A236629 A019966 * A011178 A136790 A073158

Adjacent sequences:  A021405 A021406 A021407 * A021409 A021410 A021411

KEYWORD

nonn,cons,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified January 17 16:31 EST 2021. Contains 340246 sequences. (Running on oeis4.)