[Jprogramming] Takes from a mystery sequence

[Kip Murray]

Part two: If you used J to help you figure out the sequence, tell

Kip Murray wrote:
> Verb i. produces takes from the sequence of non-negative integers:
> 
>     i.20
> 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
>     i.5
> 0 1 2 3 4
>     5 {. i.20
> 0 1 2 3 4
> 
> Verb s generates takes from a mystery sequence (no peeking in Sloane, please)
> 
>     s 13
> 2 3 7 19 53 131 311 719 1619 3671 8161 17863 38873
>     s 5
> 2 3 7 19 53
>     5 {. s 13
> 2 3 7 19 53
> 
> Your mission, should you decide to accept it, is to provide a definition for s . 
>   As always, these instructions will
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