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Search: id:A091684
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| A091684 |
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Count, setting 3n to zero. |
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+0
5
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| 0, 1, 2, 0, 4, 5, 0, 7, 8, 0, 10, 11, 0, 13, 14, 0, 16, 17, 0, 19, 20, 0, 22, 23, 0, 25, 26, 0, 28, 29, 0, 31, 32, 0, 34, 35, 0, 37, 38, 0, 40, 41, 0, 43, 44, 0, 46, 47, 0, 49, 50, 0, 52, 53, 0, 55, 56, 0, 58, 59, 0, 61, 62, 0, 64, 65, 0, 67, 68, 0, 70, 71, 0, 73, 74, 0, 76, 77, 0, 79, 80
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Multiplicative with a(3^e) = 0, a(p^e) = p^e otherwise. Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu) Jun 09, 2005.
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FORMULA
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a(n)=product{k=0..2, sum{j=1..n, w(3)^(kj) }}, w(3)=e^(2*pi*i/3), i=sqrt(-1). a(n)=2n/3-n*sin(2*pi*n/3+pi/3)/sqrt(3)-n*cos(2*pi*n/3+pi/3)/3.
G.f.: [x(x^4+2x^3+2x+1)]/[(x^2+x+1)^2(x-1)^2]. - R. Stephan, Jan 29 2004
a(n)=n^3 mod 3n; - Paul Barry (pbarry(AT)wit.ie), Apr 13 2005
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CROSSREFS
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Sequence in context: A021493 A084247 A070692 this_sequence A162397 A100050 A164616
Adjacent sequences: A091681 A091682 A091683 this_sequence A091685 A091686 A091687
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KEYWORD
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nonn,mult
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jan 28 2004
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