
theorem for n be Nat holds (Rascal n).1 = 1
  proof
    let n be Nat;
    reconsider f = Rascal n as (n + 1)-element FinSequence;
    A1: dom f = Seg (n + 1) by Def1;
    1 + 0 <= 1 + n by XREAL_1:6; then
    1 in dom f by A1; then
    f.1 = (1 - 1)*(n + 1 - 1) + 1 by Def1;
    hence thesis;
  end;
