OFFSET
1,1
COMMENTS
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..5330
EXAMPLE
187 is in the sequence because 4^4 - 4^3 - 4 - 1 = 187 = 11 * 17, which is semiprime.
1073 is in the sequence because 6^4 - 6^3 - 6 - 1 = 1073 = 29 * 37, which is semiprime.
MAPLE
select(k -> numtheory:-bigomega(k)=2, [seq(x^4 - x^3 - x - 1, x=1..1000)]);
MATHEMATICA
Select[Table[n^4 - n^3 - n - 1, {n, 500}], PrimeOmega[#] == 2 &]
PROG
(PARI)
for(n=1, 10^4, p=n^2+1; q=n^2-n-1; if(isprime(p)&&isprime(q), print1(p*q, ", "))) \\ Derek Orr, Aug 09 2014
(Magma) IsSemiprime:= func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [1..400] | IsSemiprime(s) where s is n^4 - n^3 - n - 1]; // Vincenzo Librandi, Aug 10 2014
CROSSREFS
KEYWORD
nonn,less
AUTHOR
K. D. Bajpai, Aug 09 2014
STATUS
approved