A333008 Square roots of perfect squares which are sum of two nonzero pentagonal numbers (A333007).

6, 11, 14, 20, 25, 35, 39, 59, 76, 84, 85, 92, 94, 95, 96, 104, 105, 108, 116, 123, 125, 129, 133, 136, 147, 153, 157, 160, 169, 174, 181, 186, 189, 190, 192, 194, 195, 198, 200, 206, 207, 231, 232, 238, 239, 248, 256, 270, 274, 279, 283, 288, 293, 302, 304, 307, 309, 323, 326, 332, 340, 344, 346, 350, 360, 361, 363, 370, 371, 377, 385, 391, 398, 399

Offset

1,1

Links

Peter Kagey, Table of n, a(n) for n = 1..1000

Example

a(7) = 39.  a(7)^2 = 1521 = 1 + 1520.

Mathematica

Take[Union[Select[Sqrt[#]&/@(Total/@Tuples[PolygonalNumber[ 5, Range[ 400]], 2]), IntegerQ]], 80] (* Harvey P. Dale, Apr 22 2022 *)

Crossrefs

Cf. A333007 (squares), A333009 (successive differences).

Cf. A000326 (pentagonal numbers).

Sequence in context: A315384 A315385 A315386 * A315387 A106837 A315388

Adjacent sequences: A333005 A333006 A333007 * A333009 A333010 A333011

Keyword

nonn

Author

Olivier Gérard, Mar 05 2020

Status

approved