Brute force also works:
(3 : '1{I.(E.~100&{.)}.|.,".1[\0j1000 ": y')"0[ 1r7 1r11 1r13 1r17 1r19 1r23
1r29 1r31 1r37 1r41 1r43 1r47 1r53 1r59 1r61 1r67 1r71 1r73 1r79 1r83
6 2 6 16 18 22 28 15 3 5 21 46 13 58 60 33 35 8 13 41
R.E. Boss
> -----Oorspronkelijk bericht-----
> Van: Programming <[email protected]>
> Namens Skip Cave
> Verzonden: zondag 12 januari 2020 06:58
> Aan: [email protected]
> Onderwerp: Re: [Jprogramming] Decimal expansiom
>
> Found what i needed to discover the repetition index of rational decimal
> expansions.:
>
>
> *]n=. x:%p:3+i.20*
>
> *1r7 1r11 1r13 1r17 1r19 1r23 1r29 1r31 1r37 1r41 1r43 1r47 1r53 1r59 1r61
> 1r67 1r71 1r73 1r79 1r83*
>
> NB. Verb for finding repetition index:
>
>
> * rpt =.3 :'~.|-/"1]2,\I.>+./ea*./"1 ea=ea({10,.i.500)$ea{3}.0j1000":y'*
>
> * rpt ea n*
>
> *┌─┬─┬─┬──┬──┬──┬──┬──┬─┬─┬──┬──┬──┬──┬──┬──┬──┬─┬──
> ┬──┐*
>
> *│6│2│6│16│18│22│28│15│3│5│21│46│13│58│60│33│35│8│13│41│*
>
> *└─┴─┴─┴──┴──┴──┴──┴──┴─┴─┴──┴──┴──┴──┴──┴──┴──┴─┴──
> ┴──┘*
>
> Skip
>
> Skip Cave
> Cave Consulting LLC
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