A282600 - OEIS

A282600

a(n) = Sum_(k=1..phi(n)) floor(d_k/2) where d_k are the totatives of n.

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

1,5

COMMENTS

The totatives of n are the numbers k <= n with gcd(k,n) = 1.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

David Zmiaikou, Origamis and permutation groups, Thesis, 2011. See p. 65.

FORMULA

If n is odd, a(n) = A023896(n)/2 - A000010(n)/4;

If n is even, a(n) = A023896(n)/2 - A000010(n)/2.

PROG