cp's OEIS Frontend

A341673 Irregular triangle read by rows giving the strictly superior divisors of n.

%I A341673 #10 Feb 23 2021 08:30:05
%S A341673 2,3,4,5,3,6,7,4,8,9,5,10,11,4,6,12,13,7,14,5,15,8,16,17,6,9,18,19,5,
%T A341673 10,20,7,21,11,22,23,6,8,12,24,25,13,26,9,27,7,14,28,29,6,10,15,30,31,
%U A341673 8,16,32,11,33,17,34,7,35,9,12,18,36,37,19,38,13,39
%N A341673 Irregular triangle read by rows giving the strictly superior divisors of n.
%C A341673 We define a divisor d|n to be strictly superior if d > n/d. Strictly superior divisors are counted by A056924.
%e A341673 Row n = 18 lists the strictly superior divisors of 18, which are 6, 9, 18.
%e A341673 Triangle begins:
%e A341673    1: {}
%e A341673    2: 2
%e A341673    3: 3
%e A341673    4: 4
%e A341673    5: 5
%e A341673    6: 3,6
%e A341673    7: 7
%e A341673    8: 4,8
%e A341673    9: 9
%e A341673   10: 5,10
%e A341673   11: 11
%e A341673   12: 4,6,12
%e A341673   13: 13
%e A341673   14: 7,14
%e A341673   15: 5,15
%e A341673   16: 8,16
%e A341673   17: 17
%e A341673   18: 6,9,18
%e A341673   19: 19
%e A341673   20: 5,10,20
%t A341673 Table[Select[Divisors[n],#>n/#&],{n,100}]
%Y A341673 Final terms in each row (except n = 1) are A000027.
%Y A341673 Row lengths are A056924 (number of strictly superior divisors).
%Y A341673 Initial terms in each row are A140271.
%Y A341673 The weakly inferior version is A161906.
%Y A341673 The weakly superior version is A161908.
%Y A341673 Row sums are A238535.
%Y A341673 The odd terms in each row are counted by A341594.
%Y A341673 The squarefree terms in each row are counted by A341595.
%Y A341673 The prime terms in each row are counted by A341642.
%Y A341673 The strictly inferior version is A341674.
%Y A341673 A001221 counts prime divisors, with sum A001414.
%Y A341673 A038548 counts superior (or inferior) divisors.
%Y A341673 A207375 list central divisors.
%Y A341673 - Inferior: A033676, A063962, A066839, A069288, A217581, A333749, A333750.
%Y A341673 - Superior: A033677, A051283, A059172, A063538, A063539, A070038, A072500, A116882, A116883, A341591, A341592, A341593, A341675, A341676.
%Y A341673 - Strictly Inferior: A060775, A070039, A333805, A333806, A341596, A341677.
%Y A341673 - Strictly Superior: A048098, A064052, A341643, A341644, A341646.
%Y A341673 Cf. A000005, A000203, A001222, A001248, A006530, A020639.
%K A341673 nonn,tabf
%O A341673 1,1
%A A341673 _Gus Wiseman_, Feb 22 2021