Numbers that are 2-persistent but not 3-persistent.

Terms

a(0) =1023456789a(1) =1023456879a(2) =1023457689a(3) =1023457869a(4) =1023458679a(5) =1023458769a(6) =1023465789a(7) =1023465879a(8) =1023467589a(9) =1023467859a(10) =1023468579a(11) =1023468759a(12) =1023475689a(13) =1023475869a(14) =1023476589a(15) =1023476859a(16) =1023478569a(17) =1023478659a(18) =1023485679a(19) =1023485769a(20) =1023486579a(21) =1023486759