A177087 Semiprimes of the form n^5-n^3-2*n^2+1.

2951, 16367, 58159, 159479, 368759, 534689, 1414367, 2468519, 3191201, 11862449, 14327767, 20485079, 28597439, 45393809, 102332801, 115783919, 130613617, 146925239, 282352799, 312370001, 344887399, 418040999, 459001729

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

2951=5^5-5^3-2*5^2+1 is in the sequence because 2951=13*227 and 13, 227 are primes;
58159=9^5-9^3-2*9^2+1 is in the sequence because 58159=19*3061 and 19, 3061 are primes, etc.

Mathematica

f[n_] := Last/@FactorInteger[n] == {1, 1}; Select[Array[#^5 - #^3 - 2*#^2 + 1 &, 100], f[#] &] (* Vincenzo Librandi, Sep 21 2012 *)
Select[Table[n^5 - n^3 - 2 n^2 + 1, {n, 60}], PrimeOmega[#] == 2 &] (* Bruno Berselli, Sep 21 2012 *)

Prog

(Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [2..60] | IsSemiprime(s) where s is n^5-n^3-2*n^2+1]; // Bruno Berselli, Sep 21 2012

Crossrefs

Cf. A177075, A177076, A177088 (associated n).

Sequence in context: A259999 A096628 A051024 * A125907 A025514 A204393

Adjacent sequences: A177084 A177085 A177086 * A177088 A177089 A177090

Keyword

nonn,easy

Author

Vincenzo Librandi, Jun 05 2010

Extensions

Checked by Jud McCranie, Jun 16 2010

Status

approved