OFFSET
0,2
COMMENTS
Never prime, as a(n) = (2n + 1) * (n^16 + 8n^15 + 64n^14 + 308n^13 + 1036n^12 + 2576n^11 + 4900n^10 + 7274n^9 + 8518n^8 + 7896n^7 + 5776n^6 + 3300n^5 + 1444n^4 + 468n^3 + 106n^2 + 15n + 1). Semiprime for n in {1, 5, 21, 29, 33, ...}. - Jonathan Vos Post, Aug 27 2011
REFERENCES
B. K. Teo and N. J. A. Sloane, Magic numbers in polygonal and polyhedral clusters, Inorgan. Chem. 24 (1985), 4545-4558.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
PROG
(Magma) [(n+1)^17+n^17: n in [0..20]]; // Vincenzo Librandi, Aug 28 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved