A118488 Squares for which the sum of the digits is a triangular number.

0, 1, 64, 100, 361, 1225, 2116, 3025, 5041, 6400, 10000, 17956, 18496, 21025, 23104, 26569, 29584, 32041, 36100, 38809, 47089, 54289, 58564, 59536, 63001, 68644, 69696, 77284, 82369, 87616, 88804, 94249, 110224, 117649, 122500, 128881, 130321

Offset: 1

Author

Luc Stevens (lms022(AT)yahoo.com), May 05 2006

Keywords

• base
• nonn

Examples

			26569 = 163^2 is in the sequence because it is a square and the sum of its digits, 2+6+5+6+9 = 28, is a triangular number.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A000290 and A187744.

Cf. A000217.

Programs

Mathematica

Select[Range[0, 361]^2, IntegerQ @ Sqrt[8 * Plus @@ IntegerDigits[#] + 1] &] (* Amiram Eldar, Mar 24 2021 *)

PARI

isok(n) = issquare(n) && ispolygonal(sumdigits(n), 3); \\ Michel Marcus, Feb 27 2014