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A161908 Array read by rows in which row n lists the divisors of n that are >= sqrt(n).

%I A161908 #21 Mar 08 2021 09:19:30
%S A161908 1,2,3,2,4,5,3,6,7,4,8,3,9,5,10,11,4,6,12,13,7,14,5,15,4,8,16,17,6,9,
%T A161908 18,19,5,10,20,7,21,11,22,23,6,8,12,24,5,25,13,26,9,27,7,14,28,29,6,
%U A161908 10,15,30,31,8,16,32,11,33,17,34,7,35,6,9,12,18,36,37,19,38,13,39,8,10,20,40,41,7,14,21,42,43,11,22,44,9,15,45,23,46,47,8,12,16
%N A161908 Array read by rows in which row n lists the divisors of n that are >= sqrt(n).
%C A161908 T(n,A038548(n)) = n. - _Reinhard Zumkeller_, Mar 08 2013
%C A161908 If we define a divisor d|n to be superior if d >= n/d, then superior divisors are counted by A038548 and listed by this sequence. - _Gus Wiseman_, Mar 08 2021
%H A161908 Reinhard Zumkeller, <a href="/A161908/b161908.txt">Rows n = 1..1000 of triangle, flattened</a>
%e A161908 Array begins:
%e A161908 1;
%e A161908 2;
%e A161908 3;
%e A161908 2,4;
%e A161908 5;
%e A161908 3,6;
%e A161908 7;
%e A161908 4,8;
%e A161908 3,9;
%e A161908 5,10;
%e A161908 11;
%e A161908 4,6,12;
%e A161908 13;
%e A161908 7,14;
%e A161908 5,15;
%e A161908 4,8,16;
%t A161908 Table[Select[Divisors[n],#>=Sqrt[n]&],{n,100}]//Flatten (* _Harvey P. Dale_, Jan 01 2021 *)
%o A161908 (Haskell)
%o A161908 a161908 n k = a161908_tabf !! (n-1) !! (k-1)
%o A161908 a161908_row n = a161908_tabf !! (n-1)
%o A161908 a161908_tabf = zipWith
%o A161908                (\x ds -> reverse $ map (div x) ds) [1..] a161906_tabf
%o A161908 -- _Reinhard Zumkeller_, Mar 08 2013
%Y A161908 Final terms are A000027.
%Y A161908 Initial terms are A033677.
%Y A161908 Row lengths are A038548 (number of superior divisors).
%Y A161908 Row sums are A070038 (sum of superior divisors).
%Y A161908 The inferior version is A161906.
%Y A161908 The prime terms are counted by A341591.
%Y A161908 The squarefree terms are counted by A341592.
%Y A161908 The prime-power terms are counted by A341593.
%Y A161908 The strictly superior version is A341673.
%Y A161908 The strictly inferior version is A341674.
%Y A161908 The odd terms are counted by A341675.
%Y A161908 A001221 counts prime divisors, with sum A001414.
%Y A161908 A056924 counts strictly superior (or strictly inferior divisors).
%Y A161908 A207375 lists central divisors.
%Y A161908 - Inferior: A033676, A063962, A066839, A069288, A217581, A333749, A333750.
%Y A161908 - Superior: A051283, A059172, A063538, A063539, A072500, A116882, A116883, A341592, A341676.
%Y A161908 - Strictly Inferior: A060775, A070039, A333805, A333806, A341596, A341677.
%Y A161908 - Strictly Superior: A048098, A064052, A140271, A238535, A341594, A341595, A341642, A341643, A341644, A341645, A341646.
%Y A161908 Cf. A000005, A000203, A001055, A001248, A006530, A020639, A050320, A161901.
%K A161908 easy,nonn,tabf
%O A161908 1,2
%A A161908 _Omar E. Pol_, Jun 27 2009
%E A161908 More terms from _Sean A. Irvine_, Nov 29 2010