A282601 - OEIS

A282601

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

0, 0, 0, 0, 1, 0, 2, 1, 3, 1, 6, 2, 9, 3, 6, 6, 16, 5, 20, 8, 14, 10, 30, 10, 29, 15, 28, 18, 49, 14, 56, 28, 38, 28, 48, 24, 81, 36, 54, 36, 100, 30, 110, 50, 64, 55, 132, 44, 124, 57, 96, 72, 169, 56, 130, 78, 122, 91, 210, 56, 225, 105, 136, 120, 186, 80, 272, 128, 182, 102

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OFFSET

1,7

COMMENTS

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

LINKS

Table of n, a(n) for n=1..70.

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

PROG

(PARI) a(n) = {vn = vector(n, k, k); vt = select(x->(gcd(x, n) == 1), vn); sum(k=1, #vt\2, vt[k]\2); }

CROSSREFS

Cf. A000010, A023896, A038566, A066840, A282600.