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A135953
(Nonprime Fibonacci numbers with prime indices) that have exactly 2 prime factors.
9
4181, 1346269, 165580141, 53316291173, 956722026041, 2504730781961, 308061521170129, 806515533049393, 14472334024676221, 1779979416004714189, 573147844013817084101, 10284720757613717413913, 26925748508234281076009
OFFSET
1,1
COMMENTS
Conjecture: All numbers in this sequence are products of two sums of two squares, e.g. 4181 = 37*113 = (1^2+6^2)*(7^2+8^2), 1346269 = 557*2417 = (14^2+19^2)*(4^2+49^2).
LINKS
MATHEMATICA
k = {}; Do[If[ !PrimeQ[Fibonacci[Prime[n]]], c = Length[FactorInteger[Fibonacci[Prime[n]]]]; If[c == 2, AppendTo[k, Fibonacci[Prime[n]]]]], {n, 1, 50}]; k
Select[Fibonacci[Prime[Range[30]]], PrimeOmega[#]==2&] (* Harvey P. Dale, Feb 18 2012 *)
KEYWORD
nonn
AUTHOR
Artur Jasinski, Dec 08 2007
STATUS
approved