%e A168368 Following is a graphic depiction of the stable connected piles of bricks for n = 0 to 9 ordered by increasing height (all piles of a given height within curly braces) and each variant of a given pattern within square brackets, where: C(k, i) is k choose i (binomial coefficient), F_n is n_th Fibonacci number [F_n = Sum_{k+i = n-1, i <= k} C(k, i)]. Also, the piles of heights 1 and 2 are grouped within parentheses (since they give the n_th Fibonacci number.) %e A168368 For n = 0, the following 0 [F_0] pile: ( { } ) %e A168368 For n = 1, the following 1 [F_1 = C(0, 0) = 1] pile: ( { |=| } ) %e A168368 For n = 2, the following 1 [F_2 = C(1, 0) = 1] pile: ( { |=|=| } ) %e A168368 For n = 3, the following 2 [F_3 = C(2, 0) + C(1, 1) = 2] piles: ( { ....... } & { .|=|. } ) ( { |=|=|=| } & { |=|=| } ) %e A168368 For n = 4, the following 4 [F_4 + 1 = (C(3, 0) + C(2, 1)) + 1 = 3 + 1] piles (where the brick on the third level is necessary for stability): ( { ......... } & { ....... & ....... } ) & { .|=|. } ( { ......... } & { .|=|... & ...|=|. } ) & { |=|=| } ( { |=|=|=|=| } & { |=|=|=| & |=|=|=| } ) & { .|=|. } %e A168368 For n = 5, the following 7 [F_5 + 2 = (C(4, 0) + C(3, 1) + C(2, 2)) + 2 = 5 + 2] piles: ( { ........... } & ( { |=|=|=|=|=| } & and { [ .|=|..... & ...|=|... & .....|=|. ] & .|=|=|. } ) & { [ |=|=|=|=| & |=|=|=|=| & |=|=|=|=| ] & |=|=|=| } ) & and (where the brick on the third level is necessary for stability) { .|=|.. & ..|=|. } { |=|=|. & .|=|=| } { .|=|=| & |=|=|. } %e A168368 For n = 6, the following 12 [F_6 + 4 = (C(5, 0) + C(4, 1) + C(3, 2)) + 4 = 8 + 4] piles: ( { ............. } & ( { |=|=|=|=|=|=| } & and { [ .|=|....... & (C(4,1) = 4 ways) & .......|=|. ] & { [ |=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=| ] & and [ .|=|=|... & .|=|.|=|. & ...|=|=|. ] } ) & [ |=|=|=|=| & |=|=|=|=| & |=|=|=|=| ] } ) & and (where 3rd level brick is necessary for stability of first and third piles, samely for 4th level brick of 4th pile) { ........ & ....... & ........ } & { .|=|. } { .|=|.... & ..|=|.. & ....|=|. } & { |=|=| } { |=|=|... & .|=|=|. & ...|=|=| } & { .|=|. } { .|=|=|=| & |=|=|=| & |=|=|=|. } & { |=|=| } %e A168368 For n = 7, the following 21 [F_7 + 8 = (C(6, 0) + C(5, 1) + C(4, 2) + C(3, 3)) + 8 = 13 + 8] piles: ( { ............... } & ( { |=|=|=|=|=|=|=| } & and { [ .|=|......... & (C(5,1) = 5 ways) & .........|=|. ] & { [ |=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=| ] & and [ .|=|=|..... & (C(4,2) = 6 ways) & .....|=|=|. ] & .|=|=|=|. } ) & [ |=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=| ] & |=|=|=|=| } ) & and (where the brick on the third level is necessary for stability of first and last piles) { [ .|=|...... & ...|=|.... & ....|=|... & ......|=|. ] & { [ |=|=|..... & ..|=|=|... & ...|=|=|.. & .....|=|=| ] & { [ .|=|=|=|=| & .|=|=|=|=| & |=|=|=|=|. & |=|=|=|=|. ] & and (where all the bricks on the third level are necessary for stability) [ .|=|.... & ....|=|. ] & .|=|=|. } & [ |=|=|=|. & .|=|=|=| ] & |=|=|=| } & [ .|=|=|=| & |=|=|=|. ] & .|=|=|. } & and (where the bricks on the third and fifth levels are necessary for stability) { .|=|. } { |=|=| } { .|=|. } { |=|=| } { .|=|. } %e A168368 For n = 8, the following 40 [F_8 + 19 = (C(7, 0) + C(6, 1) + C(5, 2) + C(4, 3)) + 19 = 21 + 19] piles: ( { ................. } & ( { |=|=|=|=|=|=|=|=| } & and { [ .|=|........... & (C(6,1) = 6 ways) & ...........|=|. ] & { [ |=|=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=|=| ] & and [ .|=|=|....... & (C(5,2)= 10 ways) & .......|=|=|. ] & [ |=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=| ] & and [ .|=|=|=|... & (C(4,3) = 4 ways) & ...|=|=|=|. ] } ) & [ |=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=| ] } ) & and { [ .|=|........ & . . . . . & ........|=|. ] & { [ |=|=|....... & (5 ways) & .......|=|=| ] & { [ .|=|=|=|=|=| & . . . . . & |=|=|=|=|=|. ] & and (where either |1| or |2| is a brick |=|, giving 6 ways) [ .|=|...... & ..|1|2|.. & ......|=|. ] & [ |=|=|1|2|. & .|=|=|=|. & .|2|1|=|=| ] & [ .|=|=|=|=| & |=|=|=|=| & |=|=|=|=|. ] & and (this one not contiguous on first row) .|=|.|=|. } & |=|=|=|=| } & .|=|.|=|. } & and (where either |1| or |2| is a brick |=|, giving 5 ways) { [ .|=|..... & ...|=|... & .....|=|. ] } & { [ |=|=|.... & ..|=|=|.. & ....|=|=| ] } & { [ .|=|2|... & ...|=|... & ...|2|=|. ] } & { [ |=|=|=|1| & |=|=|=|=| & |1|=|=|=| ] } & and { [ .|=|.. & ..|=|. ] } { [ |=|=|. & .|=|=| ] } { [ .|=|.. & ..|=|. ] } { | |=|=|. & .|=|=| ] } { [ .|=|=| & |=|=|. ] } %e A168368 For n = 9, the following 67 [F_9 + 33 = (C(8, 0) + C(7, 1) + C(6, 2) + C(5, 3) + C(4, 4)) + 33 = 34 + 33] piles: ( { ................... } & ( { |=|=|=|=|=|=|=|=|=| } & and { [ .|=|............. & (C(7,1) = 7 ways) & .............|=|. ] & { [ |=|=|=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=|=|=| ] & and [ .|=|=|......... & (C(6,2)= 15 ways) & .........|=|=|. ] & [ |=|=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=|=| ] & and [ .|=|=|=|..... & (C(5,3)= 10 ways) & .....|=|=|=|. ] & [ |=|=|=|=|=|=| & . . . . . . . . . & |=|=|=|=|=|=| ] & and .|=|=|=|=|. } ) & |=|=|=|=|=| } ) & and { [ .|=|.......... & . . . . . & ..........|=|. ] & { [ |=|=|......... & (6 ways) & .........|=|=| ] & { [ .|=|=|=|=|=|=| & . . . . . & |=|=|=|=|=|=|. ] & and (where either |1|, |2| or |3| is a brick |=|, giving 6 ways) [ .|=|........ & ..|1|2|.... & ..|=|...... & [ |=|=|1|2|3|. & .|=|=|=|... & .|=|=|.|=|. & [ .|=|=|=|=|=| & |=|=|=|=|=| & |=|=|=|=|=| & and (where either |1|, |2| or |3| is a brick |=|, giving 6 ways) ......|=|.. & ....|2|1|.. & ........|=|. ] } & .|=|.|=|=|. & ...|=|=|=|. & .|3|2|1|=|=| ] } & |=|=|=|=|=| & |=|=|=|=|=| & |=|=|=|=|=|. ] } & and (where either |1|, |2|, |3| or |4| is a brick |=|, giving 10 ways) { [ .|=|....... & .....|=|..... & .......|=|. ] } & { [ |=|=|...... & ....|=|=|.... & ......|=|=| ] } & { [ .|=|2|3|... & ...|3|=|4|... & ...|3|2|=|. ] } & { [ |=|=|=|=|1| & |1|=|=|=|=|2| & |1|=|=|=|=| ] } & and { [ .|=|.... & ..|=|.. & ....|=|. ] & ..|=|.. } & { [ |=|=|... & .|=|=|. & ...|=|=| ] & .|=|=|. } & { [ .|=|.... & ..|=|.. & ....|=|. ] & |=|=|=| } & { [ |=|=|... & .|=|=|. & ...|=|=| ] & .|=|=|. } & { [ .|=|=|=| & |=|=|=| & |=|=|=|. ] & ..|=|.. } & and { .|=|. } { |=|=| } { .|=|. } { |=|=| } { .|=|. } { |=|=| } %e A168368 I think I included all the stable connected piles of bricks for n=6, n=7, n=8 and n=9, please do check!