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Search: id:A132801
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| A132801 |
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a(0)=1. a(n) = sum{1<=k<=n,GCD(k,n)=1} a(floor(k/2)), where the sum is over those positive integers which are <= n and are coprime to n. |
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+0
1
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| 1, 1, 1, 2, 2, 4, 2, 7, 5, 8, 6, 17, 8, 23, 11, 20, 20, 44, 15, 57, 25, 40, 35, 94, 40, 101, 62, 114, 79, 184, 50, 215, 118, 155, 133, 247, 123, 378, 189, 311, 194, 532, 117, 597, 295, 373, 337, 801, 297, 825, 393, 741, 530, 1239, 399, 1088, 673, 1042, 833, 1871, 530
(list; graph; listen)
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OFFSET
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0,4
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EXAMPLE
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The positive integers which are <= 12 and are coprime to 12 are 1,5,7,11. Dividing each of these by 2, and rounding down, we get 0,2,3,5. So a(12) = a(0)+a(2)+a(3)+a(5) = 1+1+2+4 = 8.
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MATHEMATICA
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a = {1}; For[n = 1, n < 70, n++, s = 0; b = Select[Range[n], GCD[n, # ] == 1 &]; For[j = 1, j < Length[b] + 1, j++, s = s + a[[Floor[b[[j]]/2] + 1]]]; AppendTo[a, s]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 20 2007
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CROSSREFS
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Sequence in context: A057767 A122977 A003980 this_sequence A072478 A100577 A018818
Adjacent sequences: A132798 A132799 A132800 this_sequence A132802 A132803 A132804
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Nov 17 2007
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 20 2007
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