0,2

The sequence is unbounded.

Table of n, a(n) for n=0..29.

144 is a term as 144 + 25 ( the previous term ) = 169 is a square and also 144 + 1225 ( the next term ) = 1369 = 37^2.

a[0] = 0; a[1] = 25; a[n_] := a[n] = (k = Sqrt[a[n - 1]] + 1; While[ !IntegerQ[ Sqrt[a[n - 1] + k^2]], k++ ]; k^2); Table[ a[n], {n, 0, 30}]

Cf. A072470.

Sequence in context: A147223 A184057 A235713 * A017042 A100255 A052501

Adjacent sequences: A072468 A072469 A072470 * A072472 A072473 A072474

nonn

Amarnath Murthy, Jun 20 2002

Edited by Robert G. Wilson v, Jun 21 2002

approved