A326178 Number of subsets of {1..n} whose product is equal to their sum.

0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67

Offset

0,3

Comments

Same as A001477 (the nonnegative integers) with 3 removed.

Links

Table of n, a(n) for n=0..66.

Example

The a(1) = 1 through a(9) = 10 subsets:
  {1}  {1}  {1}      {1}      {1}      {1}      {1}      {1}      {1}
       {2}  {2}      {2}      {2}      {2}      {2}      {2}      {2}
            {3}      {3}      {3}      {3}      {3}      {3}      {3}
            {1,2,3}  {4}      {4}      {4}      {4}      {4}      {4}
                     {1,2,3}  {5}      {5}      {5}      {5}      {5}
                              {1,2,3}  {6}      {6}      {6}      {6}
                                       {1,2,3}  {7}      {7}      {7}
                                                {1,2,3}  {8}      {8}
                                                         {1,2,3}  {9}
                                                                  {1,2,3}

Mathematica

Table[Length[Select[Subsets[Range[n]], Times@@#==Plus@@#&]], {n, 0, 10}]

Crossrefs

Cf. A053632, A057567, A057568, A063865, A301987, A326156, A326158, A326179, A326180.

Sequence in context: A196252 A004722 A094798 * A162880 A083792 A083794

Adjacent sequences: A326175 A326176 A326177 * A326179 A326180 A326181

Keyword

nonn,dumb

Author

Gus Wiseman, Jun 13 2019

Status

approved