If the verb you want is repetitive double - 1 then 5 (1 -~ +:@])^:(<@[) 4 4 7 13 25 49
Otherwise, Mike's 2 at a time approach is the way to go. ________________________________ From: Skip Cave <[email protected]> To: "[email protected]" <[email protected]> Sent: Tuesday, November 27, 2018 2:10 AM Subject: [Jprogramming] Recursive verbs How would you write an implicit or explicit recursive verb for this sequence formula? a1=.4 a1 , (a2=.1-~2*a1) , (a3=.1+~2*a2) , (a4=.1-~2*a3) , (a5=.1+~2*a4) ... (an=.1(+-)~2*an-1 The verb would be specified as x f y, where x is the starting integer a1, and y is the number of terms (n) - or vice versa. The result will be a vector n items long. Note the alternating sign in each term Example: 4 f 5 4 7 15 29 59 Skip ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
