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 A161908 Array read by rows in which row n lists the divisors of n that are >= sqrt(n). 37
 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, 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, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS T(n,A038548(n)) = n. - Reinhard Zumkeller, Mar 08 2013 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 LINKS Reinhard Zumkeller, Rows n = 1..1000 of triangle, flattened EXAMPLE Array begins: 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; MATHEMATICA Table[Select[Divisors[n], #>=Sqrt[n]&], {n, 100}]//Flatten (* Harvey P. Dale, Jan 01 2021 *) PROG (Haskell) a161908 n k = a161908_tabf !! (n-1) !! (k-1) a161908_row n = a161908_tabf !! (n-1) a161908_tabf = zipWith                (\x ds -> reverse \$ map (div x) ds) [1..] a161906_tabf -- Reinhard Zumkeller, Mar 08 2013 CROSSREFS Final terms are A000027. Initial terms are A033677. Row lengths are A038548 (number of superior divisors). Row sums are A070038 (sum of superior divisors). The inferior version is A161906. The prime terms are counted by A341591. The squarefree terms are counted by A341592. The prime-power terms are counted by A341593. The strictly superior version is A341673. The strictly inferior version is A341674. The odd terms are counted by A341675. A001221 counts prime divisors, with sum A001414. A056924 counts strictly superior (or strictly inferior divisors). A207375 lists central divisors. - Inferior: A033676, A063962, A066839, A069288, A217581, A333749, A333750. - Superior: A051283, A059172, A063538, A063539, A072500, A116882, A116883, A341592, A341676. - Strictly Inferior: A060775, A070039, A333805, A333806, A341596, A341677. - Strictly Superior: A048098, A064052, A140271, A238535, A341594, A341595, A341642, A341643, A341644, A341645, A341646. Cf. A000005, A000203, A001055, A001248, A006530, A020639, A050320, A161901. Sequence in context: A290094 A285904 A285714 * A026358 A304098 A239690 Adjacent sequences:  A161905 A161906 A161907 * A161909 A161910 A161911 KEYWORD easy,nonn,tabf AUTHOR Omar E. Pol, Jun 27 2009 EXTENSIONS More terms from Sean A. Irvine, Nov 29 2010 STATUS approved

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Last modified May 5 18:25 EDT 2021. Contains 343572 sequences. (Running on oeis4.)