|
|
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
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
The first row of this array is row 2. The first column of this array is column 2.
|
|
LINKS
|
|
|
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
|
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|