---

This section details on the original issue you should resolve

<issue_title>test-lean fails for A041499</issue_title>
<issue_description>The test-lean command fails for A041499:

2025-12-08 15:42:49|INFO |Checking 15 terms of A041499: def a : Nat -> Int | 0 => 1 | 1 => 3 | 2 => 13 | n+3 => (a (n+2))*((Int.fdiv ((max ((Int.gcd ((Int.ofNat n)+3) 4)^2-3) 0)+1) 3)^2+(max ((Int.gcd ((Int.ofNat n)+3) 4)^2-3) 0)+3)+(a (n+1))
2025-12-08 15:42:52|ERROR|Error evaluating LEAN code: tool exited with code 1 (/home/me/loda/cache/loda-lean/Main.lean:1:84: error: failed to synthesize;   HSub Nat Nat Int; ; Hint: Additional diagnostic information may be available using the `set_option diagnostics true` command.; /home/me/loda/cache/loda-lean/Main.lean:1:136: error: failed to synthesize;   HSub Nat Nat Int; ; Hint: Additional diagnostic information may be available using the `set_option diagnostics true` command.)
terminate called after throwing an instance of 'std::runtime_error'

The program is:

; A041499: Denominators of continued fraction convergents to sqrt(266).
; Submitted by Science United
; 1,3,13,42,1357,4113,17809,57540,1859089,5634807,24398317,78829758,2546950573,7719681477,33425676481,107996710920,3489320425921,10575957988683,45793152380653,147955415130642,4780366436561197,14489054724814233,62736585335818129,202698810732268620,6549098528768413969,19849994397037510527,85949076116918456077,277697222747792878758,8972260204046290576333,27194477834886664607757,117750171543592949007361,380444992465665511629840,12291989930444889321162241,37256414783800333475116563
; Formula: a(n) = a(n-1)*(floor((max(gcd(n,4)^2-3,0)+1)/3)^2+max(gcd(n,4)^2-3,0)+3)+a(n-2), a(2) = 13, a(1) = 3, a(0) = 1
mov $1,1
mov $3,1
lpb $0
  sub $0,1
  mov $4,$2
  mov $2,$1
  mov $1,$3
  gcd $1,4
  pow $1,2
  trn $1,3
  add $1,1
  mov $5,$1
  div $1,3
  pow $1,2
  add $1,$5
  add $1,2
  mul $1,$2
  add $1,$4
  add $3,1
lpe
mov $0,$1
```</issue_description>

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