A076991 a(1) = 1, a(2) = 2, a(n) = smallest positive integer not occurring earlier such that the sum of three successive terms is a square.
1, 2, 6, 8, 11, 17, 21, 26, 34, 4, 43, 53, 25, 3, 36, 10, 18, 72, 31, 41, 9, 14, 13, 22, 29, 30, 5, 46, 49, 74, 73, 78, 45, 102, 109, 113, 67, 16, 38, 27, 35, 19, 90, 12, 42, 115, 39, 15, 142, 68, 79, 177, 33, 114, 214, 156, 71, 62, 63, 44, 37, 40, 23, 58, 88, 50, 87, 7, 75
Offset: 1
Links
- Ivan Neretin, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
a = {1, 2}; Do[s = a[[-1]] + a[[-2]]; k = Floor[Sqrt[s]] + 1; While[MemberQ[a, k^2 - s], k++]; AppendTo[a, k^2 - s], {n, 3, 70}]; a (* Ivan Neretin, May 25 2015 *)
Extensions
More terms from David Garber, Oct 30 2002