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A132273
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a(n) = sum{k=1 to n} (k-th integer from among those positive integers which are coprime to (n+1-k)).
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4
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1, 3, 7, 12, 20, 28, 41, 52, 69, 83, 103, 122, 149, 169, 197, 222, 257, 285, 322, 355, 397, 431, 477, 514, 567, 610, 662, 708, 769, 815, 882, 935, 1000, 1056, 1123, 1182, 1267, 1326, 1404, 1471, 1554, 1628, 1712, 1790, 1882, 1958, 2057, 2137, 2240
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| The integers coprime to 1 are: 1,2,3,4,5,6,... The 5th of these is 5. The integers coprime to 2 are: 1,3,5,7,9,... The 4th of these is 7. The integers coprime to 3 are: 1,2,4,5,7,... The 3rd of these is 4. The integers coprime to 4 are: 1,3,5,... The 2nd of these is 3. And the integers coprime to 5 are: 1,2,3,4,6,... The first of these is 1. So a(5) = 5 + 7 + 4 + 3 + 1 = 20.
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MATHEMATICA
| a = {}; For[n = 1, n < 50, n++, s = 0; For[k = 1, k < n + 1, k++, c = 0; i = 1; While[c < k, If[GCD[i, n + 1 - k] == 1, c++ ]; i++ ]; s = s + i - 1]; AppendTo[a, s]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 01 2007
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CROSSREFS
| Cf. A132274, A132275.
Sequence in context: A172115 A091369 A036698 * A130050 A173256 A002049
Adjacent sequences: A132270 A132271 A132272 * A132274 A132275 A132276
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Aug 16 2007
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EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 01 2007
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