OFFSET
1,2
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..121
Rémy Sigrist, PARI program for A272948
EXAMPLE
A160009 = (0,1,2,3,5,6,8,10,13,15,16,21,...), so that a = (1,2,3,4,5,7,9,12,...).
MATHEMATICA
s = {1}; nn = 60; f = Fibonacci[2 + Range[nn]]; Do[s = Union[s, Select[s*f[[i]], # <= f[[nn]] &]], {i, nn}]; s = Prepend[s, 0]; Take[s, 100] (* A160009 *)
isFibonacciQ[n_] := Apply[Or, Map[IntegerQ, Sqrt[{# + 4, # - 4} &[5 n^2]]]];
ans = Join[{{0}}, {{1}}, Table[#[[Flatten[Position[Map[Apply[Times, #] &, #], s[[n]]]][[1]]]] &[Rest[Subsets[Rest[Map[#[[1]] &, Select[Map[{#, isFibonacciQ[#]} &, Divisors[s[[n]]]], #[[2]] &]]]]]], {n, 3, 500}]]
Map[Length, ans] (* A272947 *)
Flatten[Position[Map[Length, ans], 1]] (* A272948 *)
Map[Apply[Times, #] &, Select[ans, Length[#] == 1 &]] (* A000045 *)
Map[Apply[Times, #] &, Select[ans, Length[#] == 2 &]] (* A271354 *)
Map[Apply[Times, #] &, Select[ans, Length[#] == 3 &]] (* A272949 *)
Map[Apply[Times, #] &, Select[ans, Length[#] == 4 &]] (* A272950 *)
(* Peter J. C. Moses, May 11 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, May 13 2016
EXTENSIONS
More terms from Rémy Sigrist, Mar 17 2019
STATUS
approved