A320055 Heinz numbers of sum-product knapsack partitions.

1, 2, 3, 5, 7, 11, 13, 15, 17, 19, 21, 23, 25, 29, 31, 33, 35, 37, 39, 41, 43, 47, 49, 51, 53, 55, 57, 59, 61, 65, 67, 69, 71, 73, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 101, 103, 107, 109, 111, 113, 115, 119, 121, 123, 127, 129, 131, 133, 137, 139, 141, 143

Offset

1,2

Comments

A sum-product knapsack partition is a finite multiset m of positive integers such that every sum of products of parts of any multiset partition of any submultiset of m is distinct.

The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).

Differs from A320056 in having 2, 845, ... and lacking 245, 455, 847, ....

Links

Table of n, a(n) for n=1..62.

Example

A complete list of sums of products of multiset partitions of submultisets of the partition (6,6,3) is:
            0 = 0
          (3) = 3
          (6) = 6
        (3*6) = 18
        (6*6) = 36
      (3*6*6) = 108
      (3)+(6) = 9
    (3)+(6*6) = 39
      (6)+(6) = 12
    (6)+(3*6) = 24
  (3)+(6)+(6) = 15
These are all distinct, and the Heinz number of (6,6,3) is 845, so 845 belongs to the sequence.

Mathematica

multWt[n_]:=If[n==1, 1, Times@@Cases[FactorInteger[n], {p_, k_}:>PrimePi[p]^k]];
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Select[Range[100], UnsameQ@@Table[Plus@@multWt/@f, {f, Join@@facs/@Divisors[#]}]&]

Crossrefs

Cf. A001970, A056239, A066739, A108917, A112798, A292886, A299702, A301899, A318949, A319318, A319913.

Cf. A267597, A320052, A320053, A320054, A320056, A320057, A320058.

Sequence in context: A331784 A325162 A331635 * A072697 A102553 A069161

Adjacent sequences: A320052 A320053 A320054 * A320056 A320057 A320058

Keyword

nonn

Author

Gus Wiseman, Oct 04 2018

Status

approved