A074317 Deficient Fibonacci numbers.

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

Alois P. Heinz, Table of n, a(n) for n = 1..300

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

Adjacent sequences: A074314 A074315 A074316 * A074318 A074319 A074320

Keyword

base,hard,nonn

Author

Shyam Sunder Gupta, Sep 22 2002

Status

approved