A257522 Table T(i,j) = denominator of (1/i + 1/j) = i*j/gcd(i*j,i+j) read by antidiagonals (i >= 1, j >= 1).

1, 2, 2, 3, 1, 3, 4, 6, 6, 4, 5, 4, 3, 4, 5, 6, 10, 12, 12, 10, 6, 7, 3, 15, 2, 15, 3, 7, 8, 14, 2, 20, 20, 2, 14, 8, 9, 8, 21, 12, 5, 12, 21, 8, 9, 10, 18, 24, 28, 30, 30, 28, 24, 18, 10, 11, 5, 9, 8, 35, 3, 35, 8, 9, 5, 11, 12, 22, 30, 36, 40, 42, 42, 40, 36, 30, 22, 12

Offset: 1

Author

Ivan Neretin, Apr 27 2015

Keywords

• nonn
• easy
• tabl

Comments

a(n) is a divisor of A003990(n) and a multiple of A089913(n).

Links

• Ivan Neretin, Table of n, a(n) for n = 1..5050

Crossrefs

Cf. A003991, A003990, A089913.

Programs

Mathematica

Flatten[Table[Denominator[1/i + 1/(m - i)], {m, 15}, {i, m - 1}]]