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A174571 a(4n)=n, a(4n+1)=4, a(4n+2)=1, a(4n+3)=4. 2
0, 4, 1, 4, 1, 4, 1, 4, 2, 4, 1, 4, 3, 4, 1, 4, 4, 4, 1, 4, 5, 4, 1, 4, 6, 4, 1, 4, 7, 4, 1, 4, 8, 4, 1, 4, 9, 4, 1, 4, 10, 4, 1, 4, 11, 4, 1, 4, 12, 4, 1, 4, 13, 4, 1, 4, 14, 4, 1, 4, 15, 4, 1, 4, 16, 4, 1, 4, 17, 4, 1, 4, 18, 4, 1, 4, 19, 4, 1, 4, 20, 4, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 0..16383

FORMULA

a(n) = A010685(n) if 4 does not divide n.

a(n) = 2*a(n-4) - a(n-8).

G.f.: -x*(-4 - x - 4*x^2 - x^3 + 4*x^4 + x^5 + 4*x^6) / ( (x-1)^2*(1+x)^2*(x^2+1)^2 ).

MATHEMATICA

Array[Which[OddQ@ Mod[#, 4], 4, Mod[#, 4] == 0, #/4, True, 1] &, 84, 0] (* or *)

CoefficientList[Series[-x (-4 - x - 4 x^2 - x^3 + 4 x^4 + x^5 + 4 x^6)/((x - 1)^2*(1 + x)^2*(x^2 + 1)^2), {x, 0, 83}], x] (* Michael De Vlieger, Nov 06 2018 *)

PROG

(PARI) A174571(n) = if(!(n%4), n/4, if(2==(n%4), 1, 4)); \\ Antti Karttunen, Nov 06 2018

CROSSREFS

Sequence in context: A331291 A080905 A010685 * A099301 A244971 A050347

Adjacent sequences:  A174568 A174569 A174570 * A174572 A174573 A174574

KEYWORD

nonn,easy

AUTHOR

Paul Curtz, Nov 29 2010

STATUS

approved

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Last modified April 7 13:32 EDT 2020. Contains 333305 sequences. (Running on oeis4.)