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A333297
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a(n) = Sum_{i=1..n, j=1..n, gcd(i,j)=1} i.
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1
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1, 4, 13, 25, 55, 73, 136, 184, 265, 325, 490, 562, 796, 922, 1102, 1294, 1702, 1864, 2377, 2617, 2995, 3325, 4084, 4372, 5122, 5590, 6319, 6823, 8041, 8401, 9796, 10564, 11554, 12370, 13630, 14278, 16276, 17302, 18706, 19666, 22126, 22882, 25591, 26911, 28531, 30049, 33292, 34444, 37531, 39031
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = a(n-1) + 3*n*phi(n)/2 for n > 1, a(n) = n for n <= 1.
a(n) = 1 + Sum_{k=2..n} 3*k*phi(k)/2. (End)
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MAPLE
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Vi := proc(m, n) local a, i, j; a:=0;
for i from 1 to m do for j from 1 to n do
if igcd(i, j)=1 then a:=a+i; fi; od: od: a; end;
# the diagonal :
[seq(Vi(n, n), n=1..50)];
# second Maple program:
a:= proc(n) option remember; `if`(n<2, n,
a(n-1) + 3*n*numtheory[phi](n)/2)
end:
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MATHEMATICA
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a[n_] := a[n] = If[n < 2, n, a[n - 1] + 3 n EulerPhi[n]/2];
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PROG
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(PARI) a(n)={my(s=0); for(i=1, n, for(j=1, n, if(gcd(i, j)==1, s+=i))); s};
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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