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Triangle read by rows: row n lists the nontrivial divisors of the n-th composite.
15

%I #6 Mar 29 2014 18:12:43

%S 2,2,3,2,4,3,2,5,2,3,4,6,2,7,3,5,2,4,8,2,3,6,9,2,4,5,10,3,7,2,11,2,3,

%T 4,6,8,12,5,2,13,3,9,2,4,7,14,2,3,5,6,10,15,2,4,8,16,3,11,2,17,5,7,2,

%U 3,4,6,9,12,18,2,19,3,13,2,4,5,8,10,20,2,3,6,7,14,21,2,4,11,22,3,5,9,15,2,23

%N Triangle read by rows: row n lists the nontrivial divisors of the n-th composite.

%C Row n contains row A002808(n) of table A027750.

%C T(n,k) = A027751(A002808(n),k+1), k = 1..A144925(n). - _Reinhard Zumkeller_, Mar 29 2014

%H Reinhard Zumkeller, <a href="/A163870/b163870.txt">Rows n = 1..1000 of table, flattened</a>

%e The table starts in row n=1 (with the composite 4) as

%e 2;

%e 2,3;

%e 2,4;

%e 3;

%e 2,5;

%e 2,3,4,6;

%e 2,7;

%e 3,5;

%e 2,4,8;

%e 2,3,6,9;

%e 2,4,5,10.

%o (Haskell)

%o a163870 n k = a163870_tabf !! (n-1) !! (k-1)

%o a163870_row n = a163870_tabf !! (n-1)

%o a163870_tabf = filter (not . null) $ map tail a027751_tabf

%o -- _Reinhard Zumkeller_, Mar 29 2014

%Y Cf. A027750.

%Y Cf. A144925 (row lengths), A062825 (row sums), A056608 (left edge), A160180 (right edge).

%K nonn,tabf

%O 1,1

%A _Juri-Stepan Gerasimov_, Aug 06 2009

%E Entries checked by _R. J. Mathar_, Sep 22 2009