Theorem: one_half_le_sum_primes_ge_one_div
File: Mathlib/NumberTheory/SumPrimeReciprocals.lean

Proof steps:
state_before: k : ℕ
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
tactic: set m : ℕ := 2 ^ k.primesBelow.card
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
tactic: set N₀ : ℕ := 2 * m ^ 2 with hN₀
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
tactic: let S : ℝ := ((2 * N₀).succ.primesBelow \ k.primesBelow).sum (fun p ↦ (1 / p : ℝ))
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 1 / 2 ≤ ∑ p ∈ (4 ^ (k.primesBelow.card + 1)).succ.primesBelow \ k.primesBelow, 1 / ↑p
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 1 / 2 ≤ S
tactic: suffices 1 / 2 ≤ S by
    convert this using 5
    rw [show 4 = 2 ^ 2 by norm_num, pow_right_comm]
    ring
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 1 / 2 ≤ S
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 2 * ↑N₀ ≤ ↑m * ↑(2 * N₀).sqrt + 2 * ↑N₀ * S
tactic: suffices 2 * N₀ ≤ m * (2 * N₀).sqrt + 2 * N₀ * S by
    rwa [hN₀, ← mul_assoc, ← pow_two 2, ← mul_pow, sqrt_eq', ← sub_le_iff_le_add',
      cast_mul, cast_mul, cast_pow, cast_two,
      show (2 * (2 * m ^ 2) - m * (2 * m) : ℝ) = 2 * (2 * m ^ 2) * (1 / 2) by ring,
      _root_.mul_le_mul_left <| by positivity] at this
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ 2 * ↑N₀ ≤ ↑m * ↑(2 * N₀).sqrt + 2 * ↑N₀ * S
state_after: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ ↑((2 * N₀).roughNumbersUpTo k).card ≤ 2 * ↑N₀ * S
tactic: calc (2 * N₀ : ℝ)
    _ = ((2 * N₀).smoothNumbersUpTo k).card + ((2 * N₀).roughNumbersUpTo k).card := by
        exact_mod_cast ((2 * N₀).smoothNumbersUpTo_card_add_roughNumbersUpTo_card k).symm
    _ ≤ m * (2 * N₀).sqrt + ((2 * N₀).roughNumbersUpTo k).card := by
        exact_mod_cast Nat.add_le_add_right ((2 * N₀).smoothNumbersUpTo_card_le k) _
    _ ≤ m * (2 * N₀).sqrt + 2 * N₀ * S := add_le_add_left ?_ _
state_before: k : ℕ
m : ℕ := 2 ^ k.primesBelow.card
N₀ : ℕ := 2 * m ^ 2
hN₀ : N₀ = 2 * m ^ 2
S : ℝ := ∑ p ∈ (2 * N₀).succ.primesBelow \ k.primesBelow, 1 / ↑p
⊢ ↑((2 * N₀).roughNumbersUpTo k).card ≤ 2 * ↑N₀ * S
state_after: no goals
tactic: exact_mod_cast roughNumbersUpTo_card_le' (2 * N₀) k