OFFSET
1,1
COMMENTS
The Heinz number of a partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k). This gives a bijective correspondence between positive integers and integer partitions.
We define the alternating product of a sequence (y_1,...,y_k) to be Product_i y_i^((-1)^(i-1)).
Also numbers whose multiset of prime indices has non-integer reverse-alternating product.
EXAMPLE
The terms and their reversed prime indices begin:
15: (3,2) 102: (7,2,1) 161: (9,4)
30: (3,2,1) 105: (4,3,2) 165: (5,3,2)
33: (5,2) 110: (5,3,1) 170: (7,3,1)
35: (4,3) 119: (7,4) 177: (17,2)
51: (7,2) 120: (3,2,1,1,1) 182: (6,4,1)
55: (5,3) 123: (13,2) 186: (11,2,1)
60: (3,2,1,1) 132: (5,2,1,1) 187: (7,5)
66: (5,2,1) 135: (3,2,2,2) 190: (8,3,1)
69: (9,2) 138: (9,2,1) 201: (19,2)
70: (4,3,1) 140: (4,3,1,1) 203: (10,4)
77: (5,4) 141: (15,2) 204: (7,2,1,1)
85: (7,3) 143: (6,5) 205: (13,3)
91: (6,4) 145: (10,3) 209: (8,5)
93: (11,2) 154: (5,4,1) 210: (4,3,2,1)
95: (8,3) 155: (11,3) 215: (14,3)
For example, (4,3,2,1) has alternating product 4/3*2/1 = 8/3, so the Heinz number 210 is in the sequence.
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
altprod[q_]:=Product[q[[i]]^(-1)^(i-1), {i, Length[q]}];
Select[Range[100], !IntegerQ[altprod[Reverse[primeMS[#]]]]&]
CROSSREFS
Factorizations not of this type are counted by A347437.
Partitions not of this type are counted by A347446.
The complement of the reverse reciprocal version is A347451.
The complement in the odd-length case is A347453.
The complement of the reverse version is A347454.
The complement is A347457.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 04 2021
STATUS
approved