convert 9j cached binomial return to BigInt. Increase 9j testing size.

src/WignerSymbols.jl

@@ -489,12 +489,12 @@ end
 bcache = LRU{Tuple{BigInt, BigInt}, BigInt}(; maxsize=10^6)
 function cbinomial(n::BigInt, k::BigInt)
     if k == 0
-        return 1 // big(1)
+        return big(1)
     end # guard
     if haskey(bcache, (n, k))
         return bcache[(n, k)]
     else
-        res = ((n + 1 - k) // k) * cbinomial(n, k - 1)
+        res = convert(BigInt, cbinomial(n, k - 1) * (n + 1 - k) // k)
         bcache[(n, k)] = res
         return res
     end

test/runtests.jl

@@ -211,7 +211,7 @@ end
 
 @threads for i = 1:N
     @testset "wigner9j: relation to sum over 6j products, thread $i" begin
-        for k = 1:1000
+        for k = 1:10_000
             @testset let (j1, j2, j3, j4, j5, j6, j7, j8, j9) = rand(smalljlist, 9)
                 @test wigner9j(j1, j2, j3, 
                            j4, j5, j6,