A130451 - OEIS

%I #10 Jan 27 2024 10:33:06

%S 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,

%T 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,

%U 8,2,3,8,2,8,2,2,8,8,8,8

%N Number of divisors of A123193(n).

%F a(n)=A000005(A123193(n)). - _R. J. Mathar_, Nov 16 2007

%p 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

%t FibQ[n_] := IntegerQ[Sqrt[5 n^2 + 4]] || IntegerQ[Sqrt[5 n^2 - 4]];

%t Select[DivisorSigma[0, Range[250]], FibQ] (* _Jean-François Alcover_, Jan 27 2024 *)

%K easy,nonn

%O 1,2

%A _Giovanni Teofilatto_, Aug 08 2007

%E Corrected and extended by _R. J. Mathar_, Nov 16 2007