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