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%I #10 Mar 07 2021 21:02:43
%S 1,1,1,1,1,2,1,1,2,1,1,2,1,1,2,3,1,1,2,1,3,1,2,1,1,2,3,1,1,2,4,1,3,1,
%T 2,1,1,2,3,4,1,1,2,1,3,1,2,4,1,1,2,3,5,1,1,2,4,1,3,1,2,1,5,1,2,3,4,1,
%U 1,2,1,3,1,2,4,5,1,1,2,3,6,1,1,2,4,1,3
%N Irregular triangle read by rows giving the strictly inferior divisors of n.
%C We define a divisor d|n to be strictly inferior if d < n/d. The number of strictly inferior divisors of n is A056924(n).
%e Triangle begins:
%e 1: {} 16: 1,2 31: 1
%e 2: 1 17: 1 32: 1,2,4
%e 3: 1 18: 1,2,3 33: 1,3
%e 4: 1 19: 1 34: 1,2
%e 5: 1 20: 1,2,4 35: 1,5
%e 6: 1,2 21: 1,3 36: 1,2,3,4
%e 7: 1 22: 1,2 37: 1
%e 8: 1,2 23: 1 38: 1,2
%e 9: 1 24: 1,2,3,4 39: 1,3
%e 10: 1,2 25: 1 40: 1,2,4,5
%e 11: 1 26: 1,2 41: 1
%e 12: 1,2,3 27: 1,3 42: 1,2,3,6
%e 13: 1 28: 1,2,4 43: 1
%e 14: 1,2 29: 1 44: 1,2,4
%e 15: 1,3 30: 1,2,3,5 45: 1,3,5
%t Table[Select[Divisors[n],#<n/#&],{n,100}]
%Y Initial terms are A000012.
%Y Row lengths are A056924 (number of strictly inferior divisors).
%Y Final terms are A060775.
%Y Row sums are A070039 (sum of strictly inferior divisors).
%Y The weakly inferior version is A161906.
%Y The weakly superior version is A161908.
%Y The odd terms are counted by A333805.
%Y The prime terms are counted by A333806.
%Y The squarefree terms are counted by A341596.
%Y The strictly superior version is A341673.
%Y The prime-power terms are counted by A341677.
%Y A001221 counts prime divisors, with sum A001414.
%Y A001222 counts prime-power divisors.
%Y A005117 lists squarefree numbers.
%Y A038548 counts superior (or inferior) divisors.
%Y A207375 lists central divisors.
%Y - Inferior: A033676, A063962, A066839, A069288, A217581, A333749, A333750.
%Y - Superior: A033677, A051283, A059172, A063538, A063539, A070038, A116882, A116883, A341591, A341592, A341593, A341675, A341676.
%Y - Strictly Superior: A048098, A064052, A140271, A238535, A341594, A341595, A341642, A341643, A341644, A341645, A341646.
%Y Cf. A000005, A000203, A001055, A001248, A006530, A020639, A050320.
%K nonn,tabf
%O 1,6
%A _Gus Wiseman_, Feb 23 2021
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