A011947 Number of Barlow packings with group P63/mmc(O) that repeat after 4n+2 layers.

1, 1, 3, 7, 14, 31, 63, 123, 255, 511, 1015, 2047, 4092

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

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