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A011947
Number of Barlow packings with group P63/mmc(O) that repeat after 4n+2 layers.
3
1, 1, 3, 7, 14, 31, 63, 123, 255, 511, 1015, 2047, 4092
OFFSET
0,3
COMMENTS
Apparently identical to A129629.
REFERENCES
T. J. McLarnan, The numbers of polytypes ..., Zeits. Krist. 155, 269-291 (1981).
FORMULA
Conjecture: a(n) = A045683(2n+1). - R. J. Mathar, Apr 15 2024
CROSSREFS
Sequence in context: A173010 A036892 A123707 * A129629 A354463 A223136
KEYWORD
nonn,easy
AUTHOR
STATUS
approved