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A132658
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a(6n+k) = 3a(6n+k-1)-3a(6n+k-2)+2a(6n+k-3), k = 0, 1, 3, 4, 5; a(6n+2) = 3a(6n+1)-3a(6n). a(0) = a(1) = 0, a(2) = 1.
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3
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0, 0, 1, 3, 6, 11, 21, 42, 63, 105, 210, 441, 903, 1806, 2709, 4515, 9030, 18963, 38829, 77658, 116487, 194145, 388290, 815409, 1669647, 3339294, 5008941, 8348235, 16696470, 35062587, 71794821, 143589642, 215384463, 358974105, 717948210
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OFFSET
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0,4
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COMMENTS
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The third differences are 0, 0, 1, 3, 6, -11, 21, 42, 63, 105, 210, -441, ..., equal to the original sequence if each 6th term is negated.
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LINKS
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MAPLE
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option remember;
if n <=1 then
0;
elif n = 2 then
1;
elif modp(n, 6) = 2 then
3*procname(n-1)-3*procname(n-2);
else
3*procname(n-1)-3*procname(n-2)+2*procname(n-3) ;
end if;
end proc:
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MATHEMATICA
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a[n_] := a[n] = Which[n <= 1, 0, n == 2, 1, Mod[n, 6] == 2, 3a[n-1] - 3a[n-2], True, 3a[n-1] - 3a[n-2] + 2a[n-3]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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