A118234 Column 3 of triangle A118233, starting at row 1 to include leading zeros.

0, 0, 1, 2, 0, 3, 2, 2, 3, 6, 1, 7, 3, 3, 5, 10, 2, 11, 5, 5, 7, 14, 3, 13, 7, 8, 7, 18, 3, 19, 10, 9, 11, 15, 5, 23, 11, 11, 11, 26, 5, 27, 13, 11, 15, 30, 7, 27, 13, 15, 15, 34, 8, 27, 15, 17, 19, 38, 7, 39, 19, 17, 21, 31, 9, 43, 21, 21, 15, 46, 11, 47, 23, 19, 23, 39, 11, 51, 21, 26, 27

Offset

1,4

Links

Table of n, a(n) for n=1..81.

Formula

a(3*n-1) = eulerphi(3*n)/2 - 1.

Prog

(PARI) {a(n)=local(M=matrix(n+2, n+2, r, c, if(r>=c, if(gcd(r-c+1, c)==1, 1, 0)))^2); M[n, 3]}

Crossrefs

Cf. A118233.

Sequence in context: A263112 A368818 A110493 * A262771 A152039 A180196

Adjacent sequences: A118231 A118232 A118233 * A118235 A118236 A118237

Keyword

nonn

Author

Leroy Quet, Paul D. Hanna, Apr 16 2006

Status

approved