OFFSET
1,1
COMMENTS
Since n^12 + 1 = (n^4+1) * (n^8 - n^4 + 1), n^12 + 1 can be semiprime only if both n^4 + 1 and n^8 - n^4 + 1 are prime.
LINKS
Robert Price, Table of n, a(n) for n = 1..1515
EXAMPLE
2^12+1 = 4097 = 17 * 241,
6^12+1 = 2176782337 = 1297 * 1678321,
34^12+1 = 2386420683693101057 = 1336337 * 1785792568561,
1136^12+1 = 4618915067251126036363854530631172097 = 1665379926017 * 2773490297975392253706241.
MATHEMATICA
Select[ Range@3691, PrimeQ[ #^4 + 1] && PrimeQ[(#^12 + 1)/(#^4 + 1)] &] (* Robert G. Wilson v *)
Select[Range[4000], PrimeOmega[#^12+1]==2&] (* Harvey P. Dale, Jan 24 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Apr 09 2005
EXTENSIONS
a(16)-a(46) from Robert G. Wilson v, Feb 10 2006
STATUS
approved