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

Author

Olivier Gérard, Mar 05 2020

Keywords

• nonn

Examples

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

Links

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

Crossrefs

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

Cf. A000326 (pentagonal numbers).

Programs

Mathematica

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