
theorem Rascal 3 = <*1,3,3,1*>
  proof
    reconsider f = Rascal 3 as (3+1)-element FinSequence;
    dom f = Seg (3 + 1) by Def1; then
    1 in dom f & 2 in dom f & 3 in dom f & 4 in dom f; then
    f.1 = (1-1)*(3+1-1) + 1 &
    f.2 = (2-1)*(3+1-2) + 1 &
    f.3 = (3-1)*(3+1-3) + 1 &
    f.4 = (4-1)*(3+1-4) + 1 by Def1;
    hence thesis;
  end;
