

A141327


Infinite array read by antidiagonals: a(m,n) = the smallest positive integer that has a factor in common with both m and n (m >= 2, n >= 2).


7



2, 6, 6, 2, 3, 2, 10, 6, 6, 10, 2, 15, 2, 15, 2, 14, 3, 10, 10, 3, 14, 2, 21, 2, 5, 2, 21, 2, 6, 6, 14, 10, 10, 14, 6, 6, 2, 3, 2, 35, 2, 35, 2, 3, 2, 22, 6, 6, 10, 14, 14, 10, 6, 6, 22, 2, 33, 2, 15, 2, 7, 2, 15, 2, 33, 2, 26, 3, 22, 5, 3, 14, 14, 3, 5, 22, 3, 26, 2, 39, 2, 55, 2, 21, 2, 21, 2
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OFFSET

2,1


COMMENTS

The first row of this array is row 2. The first column of this array is column 2.


LINKS

Diana Mecum, Table of n, a(n) for n=2..1276


FORMULA

If gcd(m,n) = 1 then a(m,n) = smallest prime factor of m times smallest prime factor of n, if gcd(m,n) > 1 then a(m,n) = min { smallest prime factor of m times smallest prime factor of n, smallest prime factor of gcd(m,n) }.


EXAMPLE

Array begins:
2 6 2 10 2 14 2 18 ...
6 3 6 15 6 ...
2 6 2 10 ...
10 15 ...
2 ...


MATHEMATICA

Table[k = 2; While[Or[CoprimeQ[#, k], CoprimeQ[n, k]] &[m  n + 2], k++]; k, {m, 2, 14}, {n, 2, m}] // Flatten (* Michael De Vlieger, Aug 01 2017 *)


CROSSREFS

Cf. A141328, A141329. For a triangular version see A144531.
Sequence in context: A242001 A175994 A283613 * A248011 A282729 A011386
Adjacent sequences: A141324 A141325 A141326 * A141328 A141329 A141330


KEYWORD

nonn,tabl


AUTHOR

Leroy Quet, Jun 25 2008


EXTENSIONS

Edited by N. J. A. Sloane, Dec 28 2008
Extended by Ray Chandler, Jun 24 2009


STATUS

approved



