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
KEYWORD
nonn,easy
AUTHOR
STATUS
approved