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 A339960 Number of Hamiltonian circuits within parallelograms of size 8 X n on the triangular lattice. 2
 1, 1676, 183521, 20842802, 3061629439, 418172485806, 56203566442908, 7621726574570613, 1033232532941136255, 139934009951521872490, 18955155770535463735959, 2567688102114635009977537, 347811042296785583958285788, 47113523803568895604053871759, 6381875340326645360658645942215 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 2..100 Olga Bodroža-Pantić, Harris Kwong and Milan Pantić, Some new characterizations of Hamiltonian cycles in triangular grid graphs, Discrete Appl. Math. 201 (2016) 1-13. (a(n) is equal to h7(n-1) defined by this paper) M. Peto, Studies of protein designability using reduced models, Thesis, 2007. PROG (Python) # Using graphillion from graphillion import GraphSet def make_T_nk(n, k): grids = [] for i in range(1, k + 1): for j in range(1, n): grids.append((i + (j - 1) * k, i + j * k)) if i < k: grids.append((i + (j - 1) * k, i + j * k + 1)) for i in range(1, k * n, k): for j in range(1, k): grids.append((i + j - 1, i + j)) return grids def A339849(n, k): universe = make_T_nk(n, k) GraphSet.set_universe(universe) cycles = GraphSet.cycles(is_hamilton=True) return cycles.len() def A339960(n): return A339849(8, n) print([A339960(n) for n in range(2, 8)]) CROSSREFS Row 8 of A339849. Cf. A145418. Sequence in context: A188008 A145755 A252300 * A252442 A159625 A156425 Adjacent sequences: A339957 A339958 A339959 * A339961 A339962 A339963 KEYWORD nonn AUTHOR Seiichi Manyama, Dec 25 2020 STATUS approved

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Last modified July 21 18:17 EDT 2024. Contains 374475 sequences. (Running on oeis4.)