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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).

%I A384376 #9 May 30 2025 10:06:21
%S A384376 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,
%T A384376 12,2,1,2,4,6,13,25,49,86,136,177,174,118,47,14,2,1,3,5,9,18,39,79,
%U A384376 168,335,646,1147,1843,2548,2908,2420,1300,473,121,24,3,1,3,4,6,7,6,3,1
%N 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).
%H A384376 Pontus von Brömssen, <a href="/A384376/b384376.txt">Table of n, a(n) for n = 1..638</a> (first 39 rows)
%H A384376 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/JohnsonSolid.html">Johnson Solid</a>.
%H A384376 Wikipedia, <a href="https://en.wikipedia.org/wiki/List_of_Johnson_solids">List of Johnson solids</a>.
%e A384376 Triangle begins:
%e A384376   n\k| 1  2  3  4  5   6   7   8    9   10   11   12   13   14   15  16  17 18 19 20
%e A384376   ---+------------------------------------------------------------------------------
%e A384376    1 | 2  2  3  2  1
%e A384376    2 | 2  2  3  3  2   1
%e A384376    3 | 2  4  6 10 14  15   8   2    1
%e A384376    4 | 2  4  6 13 21  37  47  51   28   12    2    1
%e A384376    5 | 2  4  6 13 25  49  86 136  177  174  118   47   14    2    1
%e A384376    6 | 3  5  9 18 39  79 168 335  646 1147 1843 2548 2908 2420 1300 473 121 24  3  1
%e A384376    7 | 3  4  6  7  6   3   1
%e A384376    8 | 3  4  7 12 17  16   9   3    1
%e A384376    9 | 3  4  7 13 24  35  36  22    9    3    1
%e A384376   10 | 3  4  9 16 21  16   8   3    1
%e A384376   11 | 3  4  9 18 36  49  41  23    9    3    1
%e A384376   12 | 2  2  3  2  1
%e A384376   13 | 2  2  4  5  4   2   1
%e A384376   14 | 2  3  4  7  6   6   2   1
%e A384376   15 | 2  3  5 10 15  20  13   8    2    1
%e A384376   16 | 2  3  5 11 20  38  41  36   16    8    2    1
%e A384376   17 | 2  3  6 13 19  21  12   7    2    1
%e A384376   18 | 3  7 12 29 60 134 255 425  523  420  223   80   21    3    1
%e A384376   19 | 3  7 12 32 69 174 393 899 1856 3512 5517 6874 6173 3964 1789 615 146 30  3  1
%Y A384376 Cf. A242733 (row lengths), A384377 (row sums), A384378, A384380.
%K A384376 nonn,tabf,fini
%O A384376 1,1
%A A384376 _Pontus von Brömssen_ and _Peter Kagey_, May 28 2025