This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A347844 #11 Feb 23 2025 17:45:12
%S A347844 1,9,571,254451,793949053,17342194001493,2651651342949844915,
%T A347844 2838097493373982791359403,21263575996354049430406053548413,
%U A347844 1115175826296921591259255638404605916661,409400558616252174531470888061523725583206190339
%N A347844 a(n) is the number of (strict) chains of subspaces with ends 0 and (F_7)^n.
%H A347844 Álvar Ibeas, <a href="/A347844/b347844.txt">Table of n, a(n) for n = 1..40</a>
%F A347844 a(n) = Sum_{L partition of n} A347489(n, L) * A036038(len(L), sig(L)), where sig(L) is the partition composed by the part multiplicities of L.
%e A347844 a(3) = 571 = 1 * 1 + 57 * 2 + 456 * 1, counting:
%e A347844 the unrefined chain 0 < (F_7)^3;
%e A347844 57 chains 0 < V < (F_7)^3, with dim(V) = 1; another
%e A347844 57 chains 0 < V < (F_7)^3, with dim(V) = 2; and
%e A347844 456 chains 0 < V_1 < V_2 < (F_7)^3.
%Y A347844 Cf. A289545, A347489, A036038.
%Y A347844 Column k=7 of A381426.
%K A347844 nonn
%O A347844 1,2
%A A347844 _Álvar Ibeas_, Sep 15 2021