Search: id:A132273
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%I A132273
%S A132273 1,3,7,12,20,28,41,52,69,83,103,122,149,169,197,222,257,285,322,355,397,
%T A132273 431,477,514,567,610,662,708,769,815,882,935,1000,1056,1123,1182,1267,
%U A132273 1326,1404,1471,1554,1628,1712,1790,1882,1958,2057,2137,2240
%N A132273 a(n) = sum{k=1 to n} (k-th integer from among those positive integers 
               which are coprime to (n+1-k)).
%H A132273 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A132273 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 1st of these 
               is 1. So a(5) = 5 + 7 + 4 + 3 + 1 = 20.
%t A132273 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
%Y A132273 Cf. A132274, A132275.
%Y A132273 Sequence in context: A002498 A091369 A036698 this_sequence A130050 A002049 
               A025582
%Y A132273 Adjacent sequences: A132270 A132271 A132272 this_sequence A132274 A132275 
               A132276
%K A132273 nonn
%O A132273 1,2
%A A132273 Leroy Quet Aug 16 2007
%E A132273 More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), 
               Nov 01 2007

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