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# 8D. Arithmetic

`d0=: [: >: #:` | Add 1 to cyclic counter y with upper limit x
`d1=: +//.` | Sum items of y corresponding to keys x
`d2=: +//. {~ 'abcde'"_ i. ~.@[` | Sum y according to keys x from key set 'abcde'. (substitute your ordered keyset for 'abcde')
`d3=: +.` | Greatest common divisor of x and y
`m4=: >:@i.@(>./) |/ ]` | 1 thru max y residues of y
`m5=: 0: = m4` | Locate positive integers <: y dividing y
`d6=: +"1` | Add x to each row of y
`d7=: +` | Add list x to each column of table y
`d8=: +` | Add list y to each column of table x
`d9=: *.` | Least common multiple of x and y

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