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A161204
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a(0)=2. a(n+1)=2*a(n)+period 4:repeat -5,1,3,1.
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1
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2, -1, -1, 1, 3, 1, 3, 9, 19, 33, 67, 137, 275, 545, 1091, 2185, 4371, 8737, 17475, 34953, 69907, 139809, 279619, 559241, 1118483, 2236961, 4473923, 8947849, 17895699, 35791393, 71582787, 143165577, 286331155, 572662305, 1145324611, 2290649225, 4581298451, 9162596897
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (1,1,1,2).
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FORMULA
| First differences of A180343(n).
G.f.: ( -2+3*x-x^3+2*x^2 ) / ( (2*x-1)*(1+x)*(1+x^2) ). - R. J. Mathar, Jan 26 2011
a(n) = 4*(-1)^floor((n+1)/2)*A000034(n+1)/5+2^n/15+(-1)^n/3. - R. J. Mathar, Jan 26 2011
a(n) = a(n-4)+2^(n-4).
a(n) = a(n-2)+(-3,2,4,0,0,8,16,24,=sixth differences of A007910(n-1) = 0,0,1,2,3,6,13 or fifth differences of A007909(n); also -3,2,4,8*A007910(n-1)).
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MAPLE
| A000034 := proc(n) if type(n, 'even') then 1 ; else 2 ; end if; end proc:
A161204 := proc(n) 4*(-1)^floor((n+1)/2)*A000034(n+1)/5+2^n/15+(-1)^n/3 ; end proc: # R. J. Mathar, Jan 26 2011
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CROSSREFS
| Sequence in context: A091981 A060247 A060246 * A123541 A090379 A077254
Adjacent sequences: A161201 A161202 A161203 * A161205 A161206 A161207
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KEYWORD
| sign,easy
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Jan 20 2011
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