
theorem Rascal 5 = <*1,5,7,7,5,1*>
  proof
    reconsider f = Rascal 5 as (5+1)-element FinSequence;
    dom f = Seg (5 + 1) by Def1; then
    1 in dom f & 2 in dom f & 3 in dom f &
      4 in dom f & 5 in dom f & 6 in dom f; then
    f.1 = (1-1)*(5+1-1) + 1 &
    f.2 = (2-1)*(5+1-2) + 1 &
    f.3 = (3-1)*(5+1-3) + 1 &
    f.4 = (4-1)*(5+1-4) + 1 &
    f.5 = (5-1)*(5+1-5) + 1 &
    f.6 = (6-1)*(5+1-6) + 1 by Def1;
    hence thesis;
  end;
