lean_workbook_plus_77328

⚠️ Retired — specification defect

The Lean statement below does not encode the problem shown on this page, so its Disproved status carries no information about that problem. Do not import this node or use it as a dependency.

The last digit of the natural number $n^{9102}$ is $9$ . Determine the last digit of the number $n^{2019}$ .

Why this node was retired

The posted statement is

theorem lean_workbook_plus_77328 (n : ℕ) (hn : n^9102 % 10 = 9) : n^2019 % 10 = 9   :=  by sorry

Conclude that the last digit of n^2019 is3 or7; n^9102 ending in9 forces n to end in3 or7 and does not choose between them.

The recorded counterexample refutes the statement as encoded. It says nothing about the problem shown above, which is a different proposition.

Proposed corrected statement

Conclude that the last digit of n^2019 is3 or7; n^9102 ending in9 forces n to end in3 or7 and does not choose between them.

Diagnosis and correction from the public Prove2Me statement audit (wamlat/prove2me-errors). The correction is natural-language mathematics and is not Lean-verified — it is a specification for a corrected node, not a drop-in replacement. No corrected replacement node exists yet.