hail: (1<){:[x!2;1+3*x;_ x%2]}\
  seqn: hail 27

  #seqn
112
  4#seqn
27 82 41 124
  -4#seqn
8 4 2 1

  {m,x@s?m:|/s:{#hail x}'x}{x@&x!2}!:1e5
351 77031