OFFSET
1,3
COMMENTS
A000005(a(n)) is a Fibonacci number.
For the terms shown here (in the Data section) the number of divisors is 1 or 2 or 8. - Emeric Deutsch, May 12 2008
Up to n = 104 the number of divisors is still 1, 2 or 8. - Amiram Eldar, Oct 15 2019
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..104
MAPLE
A000045 := proc(n) option remember ; coeftayl( x/(1-x-x^2), x=0, n) ; end: isA000045 := proc(n) local a; for a from 0 do if A000045(a) > n then RETURN(false) ; elif A000045(a)=n then RETURN(true) ; fi ; od: end: A000005 := proc(n) numtheory[tau](n) ; end: isA139589 := proc(n) RETURN(isA000045(n) and isA000045(A000005(n))) ; end: for i from 1 to 130 do a000045 := A000045(i) ; if isA139589(a000045) then printf("%d, ", a000045) ; fi ; od: # R. J. Mathar, May 11 2008
with(combinat): with(numtheory): F:={seq(fibonacci(k), k=1..100)}: a:=proc(n) if member(tau(fibonacci(n)), F)=true then fibonacci(n) else end if end proc: seq(a(n), n=1..70); # Emeric Deutsch, May 12 2008
MATHEMATICA
With[{s = Array[Fibonacci, 80]}, Select[s, ! FreeQ[s, DivisorSigma[0, #]] &]] (* Michael De Vlieger, Oct 15 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, May 09 2008
EXTENSIONS
More terms from R. J. Mathar and Emeric Deutsch, May 11 2008
STATUS
approved