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A186688 Semiprimes of the form n^4 + 1. 2

%I

%S 82,626,2402,4097,10001,14642,20737,28562,38417,83522,104977,194482,

%T 234257,279842,456977,707282,810001,1048577,1500626,1679617,2085137,

%U 2313442,2560001,3111697,6250001,7311617,10556002,11316497,13845842,14776337,17850626,21381377,25411682

%N Semiprimes of the form n^4 + 1.

%H Vincenzo Librandi, <a href="/A186688/b186688.txt">Table of n, a(n) for n = 1..1000</a>

%e 4097 is a member because 4097 = 8^4 + 1 = 17*241.

%t semiPrimeQ[n_] := Total[FactorInteger[n]][[2]] == 2; Select[ Range[200]^4

%t +1, semiPrimeQ]

%t Select[Table[n^4 + 1, {n, 80}], PrimeOmega[#] == 2&] (* _Vincenzo Librandi_, Sep 22 2012 *)

%o (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

%Y Cf. A144255.

%K nonn,easy

%O 1,1

%A _Michel Lagneau_, Feb 25 2011

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Last modified October 4 21:22 EDT 2022. Contains 357240 sequences. (Running on oeis4.)