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Number of co-balanced factorizations of n.
30

%I #20 Jun 10 2024 10:01:50

%S 1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,2,1,2,1,1,1,3,1,1,1,2,1,1,1,1,1,1,

%T 1,4,1,1,1,3,1,1,1,2,2,1,1,4,1,2,1,2,1,3,1,3,1,1,1,4,1,1,2,1,1,1,1,2,

%U 1,1,1,5,1,1,2,2,1,1,1,4,1,1,1,4,1,1,1,3,1,4,1,2,1,1,1,5,1,2,2,4,1,1,1,3,1,1,1,5,1,1,1,4,1,1,1,2,2,1,1,8

%N Number of co-balanced factorizations of n.

%C We define a factorization of n into factors > 1 to be co-balanced if it has exactly A001221(n) factors.

%H Antti Karttunen, <a href="/A340596/b340596.txt">Table of n, a(n) for n = 1..65537</a>

%e The a(n) co-balanced factorizations for n = 12, 24, 36, 72, 120, 144, 180:

%e 2*6 3*8 4*9 8*9 3*5*8 2*72 4*5*9

%e 3*4 4*6 6*6 2*36 4*5*6 3*48 5*6*6

%e 2*12 2*18 3*24 2*2*30 4*36 2*2*45

%e 3*12 4*18 2*3*20 6*24 2*3*30

%e 6*12 2*4*15 8*18 2*5*18

%e 2*5*12 9*16 2*6*15

%e 2*6*10 12*12 2*9*10

%e 3*4*10 3*3*20

%e 3*4*15

%e 3*5*12

%e 3*6*10

%t facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];

%t Table[Length[Select[facs[n],Length[#]==PrimeNu[n]&]],{n,100}]

%o (PARI) A340596(n, m=n, om=omega(n)) = if(1==n,(0==om), sumdiv(n, d, if((d>1)&&(d<=m), A340596(n/d, d, om-1)))); \\ _Antti Karttunen_, Jun 10 2024

%Y Positions of terms > 1 are A126706.

%Y Positions of 1's are A303554.

%Y The version for unlabeled multiset partitions is A319616.

%Y The alt-balanced version is A340599.

%Y The balanced version is A340653.

%Y The cross-balanced version is A340654.

%Y The twice-balanced version is A340655.

%Y A001055 counts factorizations.

%Y A045778 counts strict factorizations.

%Y A316439 counts factorizations by product and length.

%Y Other balance-related sequences:

%Y - A010054 counts balanced strict partitions.

%Y - A047993 counts balanced partitions.

%Y - A098124 counts balanced compositions.

%Y - A106529 lists Heinz numbers of balanced partitions.

%Y - A340597 lists numbers with an alt-balanced factorization.

%Y - A340598 counts balanced set partitions.

%Y - A340600 counts unlabeled balanced multiset partitions.

%Y Cf. A003963, A006141, A050320, A112798, A117409, A324518, A339846, A339890, A340607, A340656, A340657.

%K nonn

%O 1,12

%A _Gus Wiseman_, Jan 15 2021

%E Data section extended up to a(120) by _Antti Karttunen_, Jun 10 2024