A072471 Squares such that the sum of two neighboring term is also a square.

0, 25, 144, 256, 900, 1600, 1764, 3136, 8100, 14400, 15876, 28224, 50176, 129600, 142884, 254016, 302500, 1742400, 1920996, 3415104, 3956121, 7033104, 8767521, 15586704, 27709696, 64834704, 94303521, 167650704, 298045696, 617621904

Offset

0,2

Comments

The sequence is unbounded.

Links

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

Example

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

Mathematica

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}]

Crossrefs

Cf. A072470.

Sequence in context: A147223 A184057 A235713 * A017042 A100255 A305269

Adjacent sequences: A072468 A072469 A072470 * A072472 A072473 A072474

Keyword

nonn

Author

Amarnath Murthy, Jun 20 2002

Extensions

Edited by Robert G. Wilson v, Jun 21 2002

Status

approved