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Search: id:A068773
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| A068773 |
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Alternating sum eulerphi(1)-eulerphi(2)+eulerphi(3)-eulerphi(4)+...+((-1)^(n+1))*eulerphi(n). |
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+0
2
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| 1, 0, 2, 0, 4, 2, 8, 4, 10, 6, 16, 12, 24, 18, 26, 18, 34, 28, 46, 38, 50, 40, 62, 54, 74, 62, 80, 68, 96, 88, 118, 102, 122, 106, 130, 118, 154, 136, 160, 144, 184, 172, 214, 194, 218, 196, 242, 226, 268, 248, 280, 256, 308, 290, 330, 306, 342, 314, 372, 356
(list; graph; listen)
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OFFSET
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1,3
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FORMULA
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a(n) = sum((-1)^(k+1)*eulerphi(k), k=1..n)
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EXAMPLE
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a(3) = eulerphi(1) - eulerphi(2) + eulerphi(3) = 1 - 1 + 2 = 2.
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PROGRAM
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(PARI) a068773(m)=local(s, n); s=0; for(n=1, m, if(n%2==0, s=s-eulerphi(n), s=s+eulerphi(n)); print1(s, ", "))
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CROSSREFS
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Cf. A000010, A067929.
Adjacent sequences: A068770 A068771 A068772 this_sequence A068774 A068775 A068776
Sequence in context: A097945 A083218 A139716 this_sequence A133168 A078909 A067458
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KEYWORD
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easy,nonn
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Feb 28 2002
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