private Int128 KSumLarge2(UInt128 x, long kmin, long kmax, long x1)
{
var s = (Int128)0;
var current = T1Wheel(x / (ulong)kmin);
for (var k = kmin; k <= kmax; k++)
{
var next = T1Wheel(x / (ulong)(k + 1));
Int128.AddProduct(ref s, current - next, m[k - x1]);
current = next;
}
return(s);
}