A108158 Triangular numbers whose 10's complements are squares.

1, 6, 36, 91, 2775, 3916, 8911, 394716, 785631, 889111, 961191, 1456071, 5539456, 7704775, 13825911, 39502716, 56440000, 76156311, 88891111, 1507087351, 1764981991, 2530200816, 2743515775, 3950582716, 5119859836, 5468017600

Offset

1,2

Links

Table of n, a(n) for n=1..26.

Example

a(5)=2775 because 10^4 - 2775 = 7225 = 85^2.

Mathematica

Select[Accumulate[Range[110000]], IntegerQ[Sqrt[10^IntegerLength[#]-#]]&] (* Harvey P. Dale, Nov 18 2021 *)

Crossrefs

Sequence in context: A207454 A213189 A080857 * A207559 A207414 A192278

Adjacent sequences: A108155 A108156 A108157 * A108159 A108160 A108161

Keyword

base,easy,nonn

Author

Jason Earls, Jul 24 2005

Status

approved