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A074317
Deficient Fibonacci numbers.
1
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 233, 377, 610, 987, 1597, 4181, 6765, 10946, 17711, 28657, 75025, 121393, 196418, 317811, 514229, 1346269, 2178309, 3524578, 5702887, 9227465, 24157817, 39088169, 63245986, 165580141, 433494437
OFFSET
1,2
COMMENTS
Intersection of A000045 and A005100. - Michel Marcus, Nov 01 2014
LINKS
EXAMPLE
a(9)=55 is a term because the sum of the aliquot divisors of 55 (which is a Fibonacci number), i.e., 1+5+11=17, is less than 55.
MATHEMATICA
DeficientQ[n_]:=DivisorSigma[1, n]<2n; a={}; Do[f=Fibonacci[n]; If[DeficientQ[f], AppendTo[a, f]], {n, 1, 10^2, 1}]; a (* Vladimir Joseph Stephan Orlovsky, Jul 25 2008 *)
Select[Fibonacci[Range[50]], DivisorSigma[1, #]<2#&] (* Harvey P. Dale, Apr 28 2012 *)
CROSSREFS
Cf. A000045 (Fibonacci), A005100 (deficient).
Sequence in context: A109609 A274162 A073958 * A077371 A077372 A147659
KEYWORD
base,hard,nonn
AUTHOR
Shyam Sunder Gupta, Sep 22 2002
STATUS
approved