Stern's diatomic array (A049456) is a triangle in which row n lists the denominators in the n-th row of the table of Farey fractions. Another version of A049456 is the Stern-Brocot sequence (A002487) which has the recurrence a(2n)=a(n), a(2n+1)=a(n)+a(n+1), with a(0)=0, a(1)=1. There are a huge number of references. Someone recently asked me about a sequence which I was able to show was equal to the number of distinct terms in the n-th row of Stern's A049456. Surprisingly, this was not in the OEIS, although it is now - see A293160: 1, 2, 3, 5, 7, 13, 20, 31, 48, 78, 118, 191, 300, 465, 734, 1175, 1850, 2926, 4597, 7296, 11552, 18278, 28863, 45832, 72356, 114742, ... Can someone find a recurrence? (The smallest positive missing number from row n is A135510, which has an 1850 reference to Eisenstein.)