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

1,3

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

Links

Table of n, a(n) for n=1..13.

Example

9446031 is triangular and 1306449 is a square.

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]]

Crossrefs

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

Sequence in context: A069376 A281570 A274042 * A270994 A162030 A184570

Adjacent sequences: A066700 A066701 A066702 * A066704 A066705 A066706

Keyword

base,nonn,more

Author

Erich Friedman, Jan 14 2002

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

Status

approved