The Catalan numbers: 1, 2, 5, 14, 42, 132,
1², 2², 3², 4², 5²
1, 4, 9, 16, 25
Last verified on 07-10-2026
Series: 2, 5, 10, 17, 26, 37, 50, 64
(1 × 1) + 1 = 2
(2 × 2) + 1 = 5
(3 × 3) + 1 = 10
(4 × 4) + 1 = 17
(5 × 5) + 1 = 26
(6 × 6) + 1 = 37
(7 × 7) + 1 = 50
(8 × 8) + 1 = 65 (not 64)
Odd one: 64
Last verified on 11-11-2026
2 + 3 = 5
5 + 7 = 12
12 + 11 = 23
23 + 15 = 38
38 + 19 = 57
57 + 23 = 80
Last verified on 31-03-2026
6-2=4, 12-6=6, 20-12=8, 30-20=10
Differences go 4, 6, 8, 10... next is 12
So 30 + 12 = 42
Last updated 07 Nov 2026 by NA
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