|
%I #12 Mar 10 2015 01:42:08
%S 3,5,7,8,10,11,12,13,14,17,18,21,22,23,26,29,30,32,35,36,38,39,40,42,
%T 50,52,57,58,61,62,65,68,71,72,73,78,81,84,86,92,94,98,100,102,103,
%U 105,108,112,113,114,115,116,119,120,122,124,128,129,130,138,146,148,152,153,158
%N Numbers n such that n^4 + 1 is a semiprime.
%C Corresponding semiprimes n^4+1 are in A186688.
%H Robert Price, <a href="/A186689/b186689.txt">Table of n, a(n) for n = 1..1500</a>
%e 3 is in the sequence because 3^4 + 1 = 82 = 2*41 is semiprime.
%t SemiPrimeQ[ n_] := (n > 1) && (2 == Plus @@ (Transpose[FactorInteger[n]][[2]]));
%t Select[Range[300], SemiPrimeQ[#^4 + 1] &]
%t Select[Range[200],PrimeOmega[#^4+1]==2&] (* _Harvey P. Dale_, Jan 27 2013 *)
%Y Cf. A001358, A006313, A085722, A103854, A104238, A104335, A105041, A105066, A105078, A105122, A105142, A105237, A104479, A104494, A104657, A105282, A186688.
%K nonn
%O 1,1
%A _Michel Lagneau_, Feb 25 2011
|
