A241670 -id:A241670 - cp's OEIS frontend

A241975 Numbers n such that n^4 - n^3 - n - 1 is a semiprime.

4, 6, 10, 14, 16, 20, 36, 40, 54, 56, 66, 84, 90, 94, 116, 126, 146, 150, 156, 160, 170, 204, 210, 260, 264, 306, 340, 350, 386, 396, 406, 420, 464, 474, 496, 570, 634, 674, 696, 700, 716, 740, 764, 780, 816, 826, 864, 890, 966, 1054, 1070, 1094, 1106, 1144

Offset: 1

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Vincenzo Librandi, Aug 10 2014

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Since n^4 - n^3 - n - 1 = (n^2 + 1)*(n^2 - n - 1), these are also numbers n such that n^2 + 1 and n^2 - n - 1 are both prime. Numbers in the intersection of A005574 and A002328. - Derek Orr, Aug 10 2014 [Sequence numbers corrected by Jens Kruse Andersen, Aug 11 2014]

Vincenzo Librandi, Table of n, a(n) for n = 1..400

Cf. A001358, A002327, A002496, A085722, A241670, A243436.

IsSemiprime:=func; [ n: n in [2..1500] | IsSemiprime(n^4 - n^3 - n - 1)];

Select[Range[2000], PrimeOmega[#^4 - #^3 - # - 1]==2 &]

for(n=1,10^4,if(isprime(n^2+1)&&isprime(n^2-n-1),print1(n,", "))) \\ Derek Orr, Aug 10 2014

cp's OEIS Frontend

A241975 Numbers n such that n^4 - n^3 - n - 1 is a semiprime.

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