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A282600
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a(n) = Sum_(k=1..phi(n)) floor(d_k/2) where d_k are the totatives of n.
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3
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0, 0, 1, 1, 4, 2, 9, 6, 12, 8, 25, 10, 36, 18, 28, 28, 64, 24, 81, 36, 60, 50, 121, 44, 120, 72, 117, 78, 196, 56, 225, 120, 160, 128, 204, 102, 324, 162, 228, 152, 400, 120, 441, 210, 264, 242, 529, 184, 504, 240, 400, 300, 676, 234, 540, 324, 504, 392, 841, 232
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OFFSET
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1,5
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COMMENTS
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The totatives of n are the numbers k <= n with gcd(k,n) = 1.
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LINKS
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FORMULA
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PROG
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(PARI) a(n) = sum(k=1, n, (k\2)*(gcd(n, k)==1));
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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