A384378 Irregular triangle read by rows: T(n,k) is the number of connected subsets of k edges (or polysticks) of the n-th Johnson solid, up to symmetries of that solid; 1 <= n <= 92, 1 <= k <= A242732(n).

2, 4, 7, 12, 10, 6, 2, 1, 2, 4, 9, 17, 28, 25, 16, 7, 2, 1, 4, 7, 20, 47, 123, 274, 531, 779, 758, 504, 241, 87, 22, 4, 1, 4, 7, 20, 51, 144, 382, 990, 2332, 4873, 8546, 11776, 11733, 8529, 4673, 1957, 639, 156, 31, 4, 1

Offset

1,1

Links

Pontus von Brömssen, Table of n, a(n) for n = 1..78 (first 5 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  4  7 12  10   6   2    1
  2  | 2  4  9 17  28  25  16    7    2    1
  3  | 4  7 20 47 123 274 531  779  758  504   241    87   22    4    1
  4  | 4  7 20 51 144 382 990 2332 4873 8546 11776 11733 8529 4673 1957 639 156 31  4  1

Crossrefs

Cf. A242732 (row lengths), A384376, A384379 (row sums), A384380.

Sequence in context: A346268 A097592 A267699 * A193841 A394573 A052474

Adjacent sequences: A384375 A384376 A384377 * A384379 A384380 A384381

Keyword

nonn,tabf,fini

Author

Pontus von Brömssen and Peter Kagey, May 28 2025

Status

approved