> 2 2 6 6 10 10 14 14 18 18 22 22... is in database? > 3 3 7 7 11 11 15 15 19 19 23 23... is in database? I hope not ! else it would be a reason to add also 2,2,2,6,6,6,101010... 2,2,2,2,6,6,6,6,10101010 2,2,2,2,2,6,6,6,6,6 ... where would we go? PS: of course it is via A016825(n\2)