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A182228
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a(0)=0, a(1)=1; for n>1, a(n) = 3*a(n-2) - a(n-1).
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0
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0, 1, -1, 4, -7, 19, -40, 97, -217, 508, -1159, 2683, -6160, 14209, -32689, 75316, -173383, 399331, -919480, 2117473, -4875913, 11228332, -25856071, 59541067, -137109280, 315732481, -727060321, 1674257764, -3855438727, 8878212019, -20444528200, 47079164257
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OFFSET
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0,4
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COMMENTS
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This is A006130 with signs on every other term. - T. D. Noe, Apr 23 2012
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LINKS
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Table of n, a(n) for n=0..31.
Index to sequences with linear recurrences with constant coefficients, signature (-1,3).
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FORMULA
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a(n) = -A140167(n). G.f. -x/ ( 1+x-3*x^2 ). - R. J. Mathar, Apr 22 2013
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PROG
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(Python)
prpr = 0
prev = 1
for i in range(2, 55):
. current = prpr*3-prev
. print current,
. prpr = prev
. prev = current
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CROSSREFS
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Sequence in context: A062306 A140167 A006130 * A182646 A190646 A220011
Adjacent sequences: A182225 A182226 A182227 * A182229 A182230 A182231
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KEYWORD
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sign,easy
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AUTHOR
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Alex Ratushnyak, Apr 19 2012
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STATUS
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approved
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