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A186688
Semiprimes of the form n^4 + 1.
2
82, 626, 2402, 4097, 10001, 14642, 20737, 28562, 38417, 83522, 104977, 194482, 234257, 279842, 456977, 707282, 810001, 1048577, 1500626, 1679617, 2085137, 2313442, 2560001, 3111697, 6250001, 7311617, 10556002, 11316497, 13845842, 14776337, 17850626, 21381377, 25411682
OFFSET
1,1
LINKS
EXAMPLE
4097 is a member because 4097 = 8^4 + 1 = 17*241.
MATHEMATICA
semiPrimeQ[n_] := Total[FactorInteger[n]][[2]] == 2; Select[ Range[200]^4
+1, semiPrimeQ]
Select[Table[n^4 + 1, {n, 80}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 22 2012 *)
PROG
(Magma) IsSemiprime:= func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [1..75] | IsSemiprime(s) where s is n^4 + 1]; // Vincenzo Librandi, Sep 22 2012
CROSSREFS
Cf. A144255.
Sequence in context: A282773 A182277 A342832 * A002309 A128959 A305682
KEYWORD
nonn,easy
AUTHOR
Michel Lagneau, Feb 25 2011
STATUS
approved