Stamp folding $s(2)$

The number of distinct ways to fold a strip of $2$ labeled stamps.

Updates

• Lower bound: $2$
  Trivial or easy according to the secondary source.
  [via Number of ways of folding a strip of n labeled stamps. - OEIS]
• Upper bound: $2$
  Trivial or easy according to the secondary source.
  [via Number of ways of folding a strip of n labeled stamps. - OEIS]