FYI:
NS record should point to FQDN (see
http://www.rfc-editor.org/rfc/rfc1035.txt, chapter 3.3.11), that may not belong to specifically this domain, which in turn must have an A record in its zone. So basically all you need is this:
seed.cryptodistributed.org. IN NS seedvps.cryptodistributed.org.
seedvps IN A a.b.c.d
and the host a.b.c.d must run your dnsseed daemon.