OFFSET
1,2
COMMENTS
Every prime > n also has this property.
If a*b is a composite number > n^2, with a <= b, then a*n and b are both > n, and one of them must be <= sqrt(n*a*b); thus n^2 is an upper bound for the numbers in row n.
LINKS
Franklin T. Adams-Watters, Rows n=1..100 of table, flattened
EXAMPLE
The table starts:
1: 1
2: 4
3: 4,6,9
4: 4,6,8
5: 6,8,9,10,15,25
6: 6,8,9,10
PROG
(PARI) arow(n)=local(v, d); v=[]; for(k=n, n^2, if(!isprime(k), d=divisors(n*k); if(n==d[(#d+1)\2], v=concat(v, [k])))); v
(Haskell)
a163925 n k = a163925_tabf !! (n-1) !! (k-1)
a163925_tabf = map a163925_row [1..]
a163925_row n = [k | k <- takeWhile (<= n ^ 2) a018252_list,
let k' = k * n, let divs = a027750_row k',
last (takeWhile ((<= k') . (^ 2)) divs) == n]
-- Reinhard Zumkeller, Mar 15 2014
CROSSREFS
KEYWORD
AUTHOR
Franklin T. Adams-Watters, Aug 06 2009
STATUS
approved