a { magic n
} (((n=2)V(n<1)V(1|n)#0),((2|n)=1),((4|n)=0),1)/error,oddn,eevn,evn
evn: a { even n
} 0
eevn: a { eeven n
} 0
oddn: a { odd n
} 0
error: 'data error'

a { odd n; c; k; m; t
} (n=1)/0,a { 1 1R1
a { t\[2](t{0,((n-2)R1),0)\[1](n+n-2)+odd n-2
a[n;] { c+(-t[1]),(m{(-k),t[4],((n+1)+k{(c-n+n-1)+(0,`1Uk)+k{I.5Xn-3)),-(t{((c{.5X1+nXn)-n+2)+I4)[3]
a[1;] { c+t[3],(-m),t[1]
a[(m{1UIn-1);n] { c+t{(1+k),t[2],-k+n+2
a[m;1] { c-t

a { eeven n; c; k; m; t
} (n=4)/0,a { 4 4R16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1
a { t\[2](t{0,((n-2)R1),0)\[1](n+n-2)+ even n-2
a[1;] { (c{n+t-1)+(t-1),(k{(-k+m-1),(`1Uk{k+n+m-1),(`1Uk{k+m),(-k{(t-n)+Im{.25Xn)),t{.5X3+nXn-2
a[n;] { c+(-t),(-k),-t-1
a[(m{1UIn-1);n] { c+t{(k+m),(-k{k+m+8),(3+t),(-2+t),(-1+t),(t-2),(t-3),(4-t),(-k{k+m),+k{(t-m+m+5)+Im{m-2
a[m;1] { c-t

a { even n; c; k; m; t
a { t\[2](t{0,((n-2)R1),0)\[1](n+n-2)+ eeven n-2
a[1;] { (c{n+t-1)+(t-1),(k{(-k+m),(k{(1+k)+Im),(-k{k+n),(-k{2+k),(1+k),(-k{t-.5Xn+4),(k+m),(-k{(t-n)+Im{.25Xn-6)),t{.5X3+nXn-2
a[n;] { c+(-t),(-k),-t-1
a[(m{1UIn-1);n] { c+t{(-k+m),(`1Uk),((`1Yk{k+m+2)-2),(k{m-k),(`1Uk),1+`1Yk{(t-m-.5Xn)+Im{1+m
a[m;1] { c-t