Hello SeqFans, concatenate a(n) to a(n+1); divide by a(n+1); remainder is a(n). S = 1, 3, 9, 11, ... Example: 13 divided by 3 leaves 1 39 divided by 9 leaves 3 911 divided by 11 leaves 9 I don't have enough terms to check if this is old hat or not, sorry. Best, É. Catapulté de mon aPhone