A023375 a(n+1) = a(n) converted to base 7 from base 4 (written in base 10).

4, 7, 10, 16, 49, 148, 742, 5938, 141808, 11802091, 4842570841, 34593916101529, 5841428292099230860, 180784187945837355598287982, 4732398970947497341225017545892387325