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Triangle read by rows: T(n, k) is the number of k-dimensional subspaces in (F_3)^n, counted up to coordinate permutation (n >= 0, 0 <= k <= n).
3

%I #13 Oct 03 2021 19:25:16

%S 1,1,1,1,3,1,1,5,5,1,1,8,16,8,1,1,11,39,39,11,1,1,15,87,168,87,15,1,1,

%T 19,176,644,644,176,19,1,1,24,338,2348,4849,2348,338,24,1,1,29,613,

%U 8137,37159,37159,8137,613,29,1,1,35,1071,27047,286747,679054,286747,27047,1071

%N Triangle read by rows: T(n, k) is the number of k-dimensional subspaces in (F_3)^n, counted up to coordinate permutation (n >= 0, 0 <= k <= n).

%C Columns can be computed by a method analogous to that of Fripertinger for isometry classes of linear codes, disallowing scalar transformation of individual coordinates.

%H Álvar Ibeas, <a href="/A347970/b347970.txt">Entries up to T(16, 7)</a>

%H H. Fripertinger, <a href="http://www.mathe2.uni-bayreuth.de/frib/codes/tables.html">Isometry classes of codes</a>

%H H. Fripertinger, <a href="http://www.mathe2.uni-bayreuth.de/frib/codes/tables_15.html">Number of the isometry classes of all ternary (n,k)-codes</a>

%H Álvar Ibeas, <a href="/A347970/a347970.txt">Column k=2 up to n=100</a>

%H Álvar Ibeas, <a href="/A347970/a347970_1.txt">Column k=3 up to n=100</a>

%H Álvar Ibeas, <a href="/A347970/a347970_2.txt">Column k=4 up to n=100</a>

%H Álvar Ibeas, <a href="/A347970/a347970_3.txt">Column k=5 up to n=100</a>

%H Álvar Ibeas, <a href="/A347970/a347970_4.txt">Column k=6 up to n=100</a>

%H Álvar Ibeas, <a href="/A347970/a347970_5.txt">Column k=7 up to n=100</a>

%e Triangle begins:

%e k: 0 1 2 3 4 5 6 7

%e -----------------------------

%e n=0: 1

%e n=1: 1 1

%e n=2: 1 3 1

%e n=3: 1 5 5 1

%e n=4: 1 8 16 8 1

%e n=5: 1 11 39 39 11 1

%e n=6: 1 15 87 168 87 15 1

%e n=7: 1 19 176 644 644 176 19 1

%e There are 4 = A022167(2, 1) one-dimensional subspaces in (F_3)^2, namely, those generated by (0, 1), (1, 0), (1, 1), and (1, 2). The first two are related by coordinate swap, while the remaining two are invariant. Hence, T(2, 1) = 3.

%Y Cf. A022167, A024206(n+1) (column k=1), A076831.

%K nonn,tabl

%O 0,5

%A _Álvar Ibeas_, Sep 21 2021