Puzzle: sequence without multiples of 3

[John Keith]

A simple program to generate the sequence, which is A001651:

Code:


\<< \-> n
  \<< 1 1 n
    START DUP 1 + DUP 2 +
    NEXT n 2 * 1 + \->LIST
  \>>
\>>

Returns 2n+1 terms. Not much use to compute f(10^6) though.