A379842 Numbers that are the sum + product of a unique set of positive integers > 1. Positions of 1 in A379679.

1, 4, 6, 8, 10, 11, 12, 16, 17, 18, 19, 22, 24, 27, 28, 30, 31, 33, 36, 42, 43, 46, 48, 49, 52, 58, 61, 63, 66, 67, 70, 73, 85, 88, 91, 97, 100, 102, 105, 108, 115, 126, 130, 141, 145, 147, 148, 162, 171, 178, 192, 205, 211, 213, 226, 262, 277, 283, 288, 291

Offset

1,2

Links

Table of n, a(n) for n=1..60.

Example

For sum + product = 29 we have two possibilities: {2,9} and {4,5}, so 29 is not in the sequence.
For sum + product = 33 we have only {2,3,4}, so 33 is in the sequence.

Mathematica

nn=100;
strfacs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[strfacs[n/d], Min@@#>d&]], {d, Rest[Divisors[n]]}]];
Join@@Position[Table[Length[Select[Join@@Array[strfacs, n], Total[#]+Times@@#==n&]], {n, nn}], 1]

Crossrefs

Positions of 1 in A379679, see A379843.

For at least one multiset we have A379839, complement A379670.

For multisets instead of sets we have A379840.

For at least one (instead of exactly one) we have A379841, complement A379680.

Arrays counting multisets by sum and product:

- partitions: A379666, antidiagonal sums A379667

- partitions without ones: A379668, antidiagonal sums A379669

- strict partitions: A379671, antidiagonal sums A379672

- strict partitions without ones: A379678, antidiagonal sums A379679.

A000041 counts integer partitions, strict A000009.

A001055 counts integer factorizations, strict A045778.

A002865 counts partitions into parts > 1, strict A025147.

A318950 counts factorizations by sum.

A326622 counts factorizations with integer mean, strict A328966.

Cf. A069016, A111133, A319000, A319057, A326152, A326178, A379720.

Sequence in context: A349707 A379839 A379841 * A272475 A184016 A075254

Adjacent sequences: A379839 A379840 A379841 * A379843 A379844 A379845

Keyword

nonn,new

Author

Gus Wiseman, Jan 14 2025

Status

approved