Cannot determine how estate gets taxed on contents of 401K that had no named beneficiary.
20 percent federal tax will be removed upon closing account, but no state taxes.
If there are state taxes, will beneficiaries absorb the tax or the estate?

You stated that there are no beneficiaries.

That being the case, the estate is the direct beneficiary, and the heirs of the estate are the indirect beneficiaries. Either way, the heirs will pay the income taxes (both state and federal) on the 401K distribution, either directly on their return or on the fiduciary return filed by the estate.

Also, if the estate was of sufficient value to trigger estate taxes (i.e., the estate's value > $2M), then estate taxes are also due. If this is the case, then the value of the 401(k) could be reduced by 45% for estate taxes and 25% or so for income taxes, leaving a pittance for the heirs.

Good point, ebaines! Had not thought of that.