OFFSET
1,1
COMMENTS
First even term is the 54th Fibonacci number. The next even term is 927372692193078999176, which is the 102nd Fibonacci number. - Alonso del Arte, Oct 11 2013
EXAMPLE
55 is in the sequence because 54 = 2 * 3^3 and 56 = 2^3 * 7 are not squarefree numbers.
89 is in the sequence because 88 = 2^3 * 11 and 90 = 2 * 3^2 * 5 are not squarefree numbers.
144 is not in the sequence because both 143 = 11 * 13 and 145 = 5 * 29 are squarefree.
MAPLE
issqrfreeneigh := proc(n) return not (issqrfree(m-1) or issqrfree(m+1)): end proc: for n from 1 to 100 do m:=combinat[fibonacci](n): if issqrfreeneigh(m) then printf("%d, ", m): end if: end do: # Nathaniel Johnston, Oct 11 2013
MATHEMATICA
Select[Fibonacci[Range[100]], Abs[MoebiusMu[# - 1]] + Abs[MoebiusMu[# + 1]] == 0 &] (* Alonso del Arte, Oct 11 2013 *)
Select[Fibonacci[Range[100]], NoneTrue[#+{1, -1}, SquareFreeQ]&] (* Harvey P. Dale, Oct 09 2021 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Juri-Stepan Gerasimov, Oct 10 2013
EXTENSIONS
a(5)-a(20) from Nathaniel Johnston, Oct 11 2013
STATUS
approved