A066703 Triangular numbers whose reverse is a square with the same number of digits.

0, 1, 9446031, 1270004401, 14214075921, 1809702709101, 4614899724711, 6766532724546, 52657436563056, 98855178542676, 520454948099628321, 467756399278821844071, 40441102744430519189191

Offset: 1

Author

Erich Friedman, Jan 14 2002

Keywords

• base
• nonn
• more

Comments

The sequence of corresponding squares is A066702. - Robert G. Wilson v, Jan 31 2011

a(14) > 2*10^24. - Giovanni Resta, Jun 20 2015

Examples

			9446031 is triangular and 1306449 is a square.
		

Crossrefs

See A179889 for another version. Cf. A066702, A069673.

Programs

Mathematica

lst = {0}; For[i=1, i<10^6, i++, t=i(i+1)/2; r=FromDigits@ Reverse@ IntegerDigits@ t; If[ Mod[t, 10] > 0 && IntegerQ@ Sqrt@ r, AppendTo[lst, t]; Print@ lst]]

Extensions

More terms from Jason Earls and the author, Jan 15 2002

Offset and definition modified at the suggestion of Harvey P. Dale, Jan 30 2011

a(11) from Donovan Johnson, Jan 31 2011

a(12)-a(13) from Giovanni Resta, Jun 20 2015