A130451 Number of divisors of A123193(n).

1, 2, 2, 3, 2, 2, 3, 2, 2, 5, 2, 2, 2, 8, 3, 2, 8, 2, 2, 8, 2, 8, 2, 2, 3, 2, 8, 8, 2, 2, 8, 2, 8, 2, 2, 8, 2, 5, 2, 8, 2, 2, 2, 8, 2, 8, 8, 2, 2, 8, 2, 8, 3, 2, 8, 8, 2, 8, 8, 2, 8, 2, 2, 2, 8, 8, 2, 2, 8, 2, 3, 8, 2, 8, 2, 2, 8, 8, 8, 8

Offset

1,2

Links

Table of n, a(n) for n=1..80.

Formula

a(n)=A000005(A123193(n)). - R. J. Mathar, Nov 16 2007

Maple

isFib := proc(n) local i ; for i from 1 do if combinat[fibonacci](i) > n then RETURN(false) ; elif combinat[fibonacci](i) = n then RETURN(true) ; fi ; od: end: A123193 := proc(n) option remember ; local nmin, k ; nmin := 1 : if n > 1 then nmin := A123193(n-1)+1 ; fi ; for k from nmin do if isFib( numtheory[tau](k) ) then RETURN(k) ; fi ; od: end: A130451 := proc(n) numtheory[tau](A123193(n)) ; end: seq(A130451(n), n=1..80) ; # R. J. Mathar, Nov 16 2007

Mathematica

FibQ[n_] := IntegerQ[Sqrt[5 n^2 + 4]] || IntegerQ[Sqrt[5 n^2 - 4]];
Select[DivisorSigma[0, Range[250]], FibQ] (* Jean-François Alcover, Jan 27 2024 *)

Crossrefs

Sequence in context: A218800 A062502 A141242 * A130285 A046027 A283671

Adjacent sequences: A130448 A130449 A130450 * A130452 A130453 A130454

Keyword

easy,nonn

Author

Giovanni Teofilatto, Aug 08 2007

Extensions

Corrected and extended by R. J. Mathar, Nov 16 2007

Status

approved