A238689 - OEIS

%I #13 Sep 16 2016 02:44:01

%S 1,2,3,2,2,5,3,2,7,2,2,2,3,3,5,2,11,3,2,2,13,7,2,5,3,2,2,2,2,17,3,3,2,

%T 19,5,2,2,7,3,11,2,23,3,2,2,2,5,5,13,2,3,3,3,7,2,2,29,5,3,2,31,2,2,2,

%U 2,2,11,3,17,2,7,5,3,3,2,2,37,19,2,13,3,5,2,2,2

%N Table read by rows: first row is {1}; for n >1, T(n, k) is the k-th largest prime factor of n (repeated prime factors are counted repeatedly).

%C n-th row has length 1 if n = 1, A001222(n) if n > 1.

%H Peter Kagey, <a href="/A238689/b238689.txt">Table of n, a(n) for n = 1..10000</a>

%F Row n is row n of A027746 in reverse order.

%e Table begins:

%e 1;

%e 2;

%e 3;

%e 2,2;

%e 5;

%e 3,2;

%e 7;

%e 2,2,2;

%e 3,3;

%e 5,2;

%e ...

%o (Haskell)

%o a238689_row 1 = [1]

%o a238689_row n = a n [] a000040_list where

%o   a m factors ps@(p:ps')

%o     | m == 1         = factors

%o     | m `mod` p == 0 = a (m `div` p) (p : factors) ps

%o     | otherwise      = a m           factors       ps'

%o a _ _ [] = [] -- _Peter Kagey_, Sep 15 2016

%Y First column is A006530; numbers along right boundary form A020639.

%Y A001414 gives row sums (for n > 1).

%Y Cf. A027746, A238690.

%K nonn,tabf

%O 1,2

%A _Matthew Vandermast_, Apr 28 2014