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A326172 Number of nonempty subsets of {2..n} whose product is divisible by their sum. 2
0, 0, 1, 2, 3, 6, 12, 21, 34, 69, 140, 278, 561, 1144, 2367, 4936, 9503, 19368, 38202, 77911, 156458, 318911, 651462, 1329624, 2596458, 5144833, 10494839, 20500025, 40923643, 83620258, 164982516, 335873558, 651383048, 1310551707, 2655240565, 5295397093, 10338145110, 21052407259, 42748787713, 86078893923, 169349494068 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..40.

EXAMPLE

The a(2) = 1 through a(7) = 21 subsets:

  {2}  {2}  {2}  {2}      {2}          {2}

       {3}  {3}  {3}      {3}          {3}

            {4}  {4}      {4}          {4}

                 {5}      {5}          {5}

                 {2,3,5}  {6}          {6}

                 {3,4,5}  {3,6}        {7}

                          {2,3,5}      {3,6}

                          {2,4,6}      {2,3,5}

                          {3,4,5}      {2,4,6}

                          {4,5,6}      {2,5,7}

                          {3,4,5,6}    {3,4,5}

                          {2,3,4,5,6}  {3,4,7}

                                       {3,5,7}

                                       {4,5,6}

                                       {2,3,6,7}

                                       {2,5,6,7}

                                       {3,4,5,6}

                                       {3,5,6,7}

                                       {2,3,4,5,6}

                                       {2,3,4,5,7}

                                       {2,4,5,6,7}

MATHEMATICA

Table[Length[Select[Subsets[Range[2, n], {1, n}], Divisible[Times@@#, Plus@@#]&]], {n, 0, 10}]

CROSSREFS

Cf. A053632, A057567, A057568, A059529, A063865, A301987, A325037, A325044, A326150, A326151, A326153/A326154, A326155, A326156, A326158, A326178.

Sequence in context: A096571 A227940 A081156 * A082877 A047090 A185265

Adjacent sequences:  A326169 A326170 A326171 * A326173 A326174 A326175

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jun 11 2019

EXTENSIONS

a(21)-a(29) from Alois P. Heinz, Jun 13 2019

a(30)-a(40) from Bert Dobbelaere, Jun 22 2019

STATUS

approved

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Last modified May 21 09:19 EDT 2022. Contains 353908 sequences. (Running on oeis4.)