OFFSET
1,1
COMMENTS
a(14) > 10^9. - Giovanni Resta, May 06 2017
EXAMPLE
F(8) = 21, 8*9/2 - sigma(8) = 21 and 21/21 = 1.
MAPLE
with(numtheory): with(combinat): P:=proc(q) local n; for n from 1 to q do
if n*(n+1)/2-sigma(n)>0 then if type(fibonacci(n)/(n*(n+1)/2-sigma(n)), integer) then print(n); fi; fi; od; end: P(10^6);
MATHEMATICA
Select[Range[3, 150000], Divisible[Fibonacci@ #, # (# + 1)/2 - DivisorSigma[1, #]] &] (* or *)
Do[If[Divisible[Fibonacci@ #, # (# + 1)/2 - DivisorSigma[1, #]] &@ n, Print@ n], {n, 3, 150000}] (* Michael De Vlieger, May 03 2017, both after Robert G. Wilson v at A024816 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, May 03 2017
EXTENSIONS
a(10)-a(12) from Robert G. Wilson v, May 06 2017
a(13) from Giovanni Resta, May 06 2017
STATUS
approved