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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
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 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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

MATHEMATICA

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

CROSSREFS

Cf. A003991, A003990, A089913.

Sequence in context: A289236 A280172 A089913 * A059897 A325821 A303719

Adjacent sequences:  A257519 A257520 A257521 * A257523 A257524 A257525

KEYWORD

nonn,easy,tabl

AUTHOR

Ivan Neretin, Apr 27 2015

STATUS

approved

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Last modified November 21 00:10 EST 2019. Contains 329348 sequences. (Running on oeis4.)