A384376 - OEIS

A384376

Irregular triangle read by rows: T(n,k) is the number of connected induced k-vertex subgraphs of the 1-skeleton of the n-th Johnson solid, up to symmetries of that solid; 1 <= n <= 92, 1 <= k <= A242733(n).

2, 2, 3, 2, 1, 2, 2, 3, 3, 2, 1, 2, 4, 6, 10, 14, 15, 8, 2, 1, 2, 4, 6, 13, 21, 37, 47, 51, 28, 12, 2, 1, 2, 4, 6, 13, 25, 49, 86, 136, 177, 174, 118, 47, 14, 2, 1, 3, 5, 9, 18, 39, 79, 168, 335, 646, 1147, 1843, 2548, 2908, 2420, 1300, 473, 121, 24, 3, 1, 3, 4, 6, 7, 6, 3, 1

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Pontus von Brömssen, Table of n, a(n) for n = 1..638 (first 39 rows)

Eric Weisstein's World of Mathematics, Johnson Solid.

Wikipedia, List of Johnson solids.

EXAMPLE

Triangle begins:

n\k| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

---+------------------------------------------------------------------------------

1 | 2 2 3 2 1

2 | 2 2 3 3 2 1

3 | 2 4 6 10 14 15 8 2 1

4 | 2 4 6 13 21 37 47 51 28 12 2 1

5 | 2 4 6 13 25 49 86 136 177 174 118 47 14 2 1

6 | 3 5 9 18 39 79 168 335 646 1147 1843 2548 2908 2420 1300 473 121 24 3 1

7 | 3 4 6 7 6 3 1

8 | 3 4 7 12 17 16 9 3 1

9 | 3 4 7 13 24 35 36 22 9 3 1

10 | 3 4 9 16 21 16 8 3 1

11 | 3 4 9 18 36 49 41 23 9 3 1

12 | 2 2 3 2 1

13 | 2 2 4 5 4 2 1

14 | 2 3 4 7 6 6 2 1

15 | 2 3 5 10 15 20 13 8 2 1

16 | 2 3 5 11 20 38 41 36 16 8 2 1

17 | 2 3 6 13 19 21 12 7 2 1

18 | 3 7 12 29 60 134 255 425 523 420 223 80 21 3 1

19 | 3 7 12 32 69 174 393 899 1856 3512 5517 6874 6173 3964 1789 615 146 30 3 1

CROSSREFS

Cf. A242733 (row lengths), A384377 (row sums), A384378, A384380.

Sequence in context: A368798 A253141 A100890 * A384380 A262815 A076494

Adjacent sequences: A384373 A384374 A384375 * A384377 A384378 A384379

KEYWORD

nonn,tabf,fini

AUTHOR

Pontus von Brömssen and Peter Kagey, May 28 2025

STATUS

approved