The sequence combines prime numbers with their position indices: 2+0=2, 3+1=4 (not 5), 5+2=7, 7+3=10, 11+4=15 (not 14), 13+5=18 (not 20). Alternative pattern: starting with 2,3,5,7 (consecutive primes), then each term adds successively larger increments (+3,+4,+6,+9). Following this: 20+9=29.