TF0009

three_mod_four_progression_not_two_square

Alpha v34 independently verified · alpha_closed; checked-use authorized; not Stable

A witnessed three-modulo-four natural cannot have a two-square representation.

Current library: Alpha v34, 4,223 checked-use theorems; Stable remains 432. Historical first admissions, original proof editions, and non-admitted aliases are preserved. Exact original first-admission records.

Exact expanded first-order arithmetic statement

forall n. (exists ff_residue_ptmf_number. (n) = 4 * ff_residue_ptmf_number + 3) -> (exists ptmf_first_represented ptmf_second_represented. (n) = ptmf_first_represented * ptmf_first_represented + ptmf_second_represented * ptmf_second_represented) -> false

Constructive proof overview

Generated structural guide

A witnessed three-modulo-four natural cannot have a two-square representation.

The unchanged tactic script uses 1 declared prerequisite and contains 9 exact native proof lines.

Alpha v34 checked-use · first admitted v23 · independently kernel and Lean verified; not Stable

Proof neighborhood

Direct dependencies

three_mod_four_number_not_equal_represented Alpha theorem; checked-use authorized

Direct dependents

Formal native tactic body

Dependencies are introduced as named hypotheses before line 1. Local theorem links identify exact declared prerequisites. This exact body belongs to a complete independently kernel-checked constructive proof bundle and has Alpha checked-use authority; it does not imply Stable membership.

Read the argument

Proof checkpoints

9 script commands · 3 reading checkpoints · 0 local claims

This is a reading aid, not a new proof or a proof-tree certificate. Checkpoint groups are consecutive commands, not inferred branch boundaries. Every step links to the preserved script.

01Fix variables and assumptionsL1–3

Work with arbitrary variables or the premises of the current implication.

  1. L1
    intro n
  2. L2
    intro hthree
  3. L3
    intro hrepresented
02Use earlier factsL4–8

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L4
    specialize three_mod_four_number_not_equal_represented n
  2. L5
    specialize three_mod_four_number_not_equal_represented n
  3. L6
    apply three_mod_four_number_not_equal_represented
  4. L7
    exact hthree
  5. L8
    exact hrepresented
03Calculate and transport equalitiesL9–9

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L9
    refl

Library-wide reading audit

Original exact command ledger · 9 lines
  1. 0001intro n
  2. 0002intro hthree
  3. 0003intro hrepresented
  4. 0004specialize three_mod_four_number_not_equal_represented n
  5. 0005specialize three_mod_four_number_not_equal_represented n
  6. 0006apply three_mod_four_number_not_equal_represented
  7. 0007exact hthree
  8. 0008exact hrepresented
  9. 0009refl