OFFSET
7,1
COMMENTS
Orthoplex polyominoes are connected sets of cells of regular tilings with Schläfli symbols {}, {4}, {3,4}, {3,3,4}, {3,3,3,4}, etc. These are tilings of regular orthoplexes projected on their circumspheres. Orthoplex polyominoes are equivalent to multidimensional polyominoes that do not extend more than two units along any axis, i.e., fit within a 2^d cube. Each member of a chiral pair is a reflection but not a rotation of the other.
LINKS
Robert A. Russell, Table of n, a(n) for n = 7..100
Robert A. Russell, Trunk Generating Functions
FORMULA
G.f.: (14 C(x)^6 + 3 C(x)^7 + 6 C(x)^4 C(-x^2) + 6 C(x)^5 C(-x^2) - 18 C(x)^2 C(-x^2)^2 + 3 C(x)^3 C(-x^2)^2 - 10 C(-x^2)^3 - 6 C(x) C(-x^2)^3 + 4 C(x^3)^2 - 6 C(x) C(-x^2) C(-x^4) + 4 C(-x^6)) / 24 + C(x)^3 (38 C(x)^4 + 9 C(x)^5 + 4 C(x)^2 C(-x^2) + 10 C(x)^3 C(-x^2) - 2 C(-x^2)^2 + C(x) C(-x^2)^2) / (8(1-C(x))) + C(x)^6 (5 C(x) + 16 C(x)^2 + 6 C(x)^3 + C(-x^2) + 2 C(x) C(-x^2)) / (2(1-C(x))^2) - C(-x^2)^2 (C(x)^4 + 2 C(x) C(-x^2) + 4 C(x)^2 C(-x^2) + 2 C(-x^2)^2 + 5 C(x) C(-x^2)^2 + C(-x^4) + C(x) C(-x^4)) / (4(1-C(-x^2))) + C(x)^7 (2 + 42 C(x) + 51 C(x)^2 + 24 C(x)^3 + 3 C(-x^2)) / (12(1-C(x))^3) + (C(x) C(x^3)^2) / (3(1-C(x^3))) - C(x)^2 C(-x^2)^2 (2 C(x) + 5 C(x)^3 + 2 C(-x^2) + C(x) C(-x^2)) / (4(1-C(x)) (1-C(-x^2))) - C(-x^2)^4 (8 + C(x) + 8 C(x) C(-x^2)) / (8(1-C(-x^2))^2) + C(x)^9 (17 + 8 C(x)) / (8(1-C(x))^4) - C(x)^5 (1 + 4 C(x)) C(-x^2)^2 / (4(1-C(x))^2 (1-C(-x^2))) + (C(x) C(-x^4)^2) / (4(1-C(-x^4))) + (3 C(x)^10) / (8(1-C(x))^5) - ((C(x)^6 C(-x^2)^2) / (4(1-C(x))^3 (1-C(-x^2)))) - (((1 + C(x)) C(-x^2)^5) / (4(1-C(-x^2))^3)) + ((1 + C(x)) C(-x^2) C(-x^4)^2) / (4(1-C(-x^2)) (1-C(-x^4))) - ((C(x)^2 C(-x^2)^4) / (8(1-C(x)) (1-C(-x^2))^2)) where C(x) is the generating function for chiral n-ominoes in n-1 space, one cell labeled in A045648.
EXAMPLE
a(7)=8 because there are 8 pairs of chiral heptominoes in 2^4 space. See trunks 1, 6, 8, 12, 13, 19, 27, and 28 in the linked Trunk Generating Functions.
MATHEMATICA
sc[n_, k_] := sc[n, k] = c[n+1-k, 1] + If[n<2k, 0, sc[n-k, k](-1)^k];
c[1, 1] := 1; c[n_, 1] := c[n, 1] = Sum[c[i, 1] sc[n-1, i]i, {i, 1, n-1}]/(n-1);
c[n_, k_] := c[n, k] = Sum[c[i, 1] c[n-i, k-1], {i, 1, n-1}];
nmax = 30; K[x_] := Sum[c[i, 1] x^i, {i, 0, nmax}]
Drop[CoefficientList[Series[(14 K[x]^6 + 3 K[x]^7 + 6 K[x]^4 K[-x^2] + 6 K[x]^5 K[-x^2] - 18 K[x]^2 K[-x^2]^2 + 3 K[x]^3 K[-x^2]^2 - 10 K[-x^2]^3 - 6 K[x] K[-x^2]^3 + 4 K[x^3]^2 - 6 K[x] K[-x^2] K[-x^4] + 4 K[-x^6]) / 24 + K[x]^3 (38 K[x]^4 + 9 K[x]^5 + 4 K[x]^2 K[-x^2] + 10 K[x]^3 K[-x^2] - 2 K[-x^2]^2 + K[x] K[-x^2]^2) / (8(1-K[x])) + K[x]^6 (5 K[x] + 16 K[x]^2 + 6 K[x]^3 + K[-x^2] + 2 K[x] K[-x^2]) / (2(1-K[x])^2) - K[-x^2]^2 (K[x]^4 + 2 K[x] K[-x^2] + 4 K[x]^2 K[-x^2] + 2 K[-x^2]^2 + 5 K[x] K[-x^2]^2 + K[-x^4] + K[x] K[-x^4]) / (4(1-K[-x^2])) + K[x]^7 (2 + 42 K[x] + 51 K[x]^2 + 24 K[x]^3 + 3 K[-x^2]) / (12(1-K[x])^3) + (K[x] K[x^3]^2) / (3(1-K[x^3])) - K[x]^2 K[-x^2]^2 (2 K[x] + 5 K[x]^3 + 2 K[-x^2] + K[x] K[-x^2]) / (4(1-K[x]) (1-K[-x^2])) - K[-x^2]^4 (8 + K[x] + 8 K[x] K[-x^2]) / (8(1-K[-x^2])^2) + K[x]^9 (17 + 8 K[x]) / (8(1-K[x])^4) - K[x]^5 (1 + 4 K[x]) K[-x^2]^2 / (4(1-K[x])^2 (1-K[-x^2])) + (K[x] K[-x^4]^2) / (4(1-K[-x^4])) + (3 K[x]^10) / (8(1-K[x])^5) - ((K[x]^6 K[-x^2]^2) / (4(1-K[x])^3 (1-K[-x^2]))) - (((1 + K[x]) K[-x^2]^5) / (4(1-K[-x^2])^3)) + ((1 + K[x]) K[-x^2] K[-x^4]^2) / (4(1-K[-x^2]) (1-K[-x^4])) - ((K[x]^2 K[-x^2]^4) / (8(1-K[x]) (1-K[-x^2])^2)), {x, 0, nmax}], x], 7]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Robert A. Russell, Jun 16 2022
STATUS
approved