A069077 Triangular numbers such that the product of digits is also a (positive) triangular number.

1, 3, 6, 66, 153, 231, 351, 465, 741, 1326, 2556, 5671, 6786, 14535, 21115, 24531, 25651, 33411, 43956, 57291, 58311, 71253, 92665, 95266, 123753, 153181, 167331, 278631, 325221, 341551, 351541, 372816, 459361, 491536, 516636, 521731, 567645

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..457

Mathematica

aQ[n_] := (p = Times @@ IntegerDigits[n]) > 0 && IntegerQ @ Sqrt[8p + 1]; t[n_] := n(n+1)/2; Select[t[Range[10^3]], aQ] (* Amiram Eldar, Aug 12 2019 *)
Select[Accumulate[Range[1500]], FreeQ[IntegerDigits[#], 0]&&OddQ[Sqrt[8 Times@@IntegerDigits[ #]+1]]&] (* Harvey P. Dale, May 01 2023 *)

Prog

(Magma) [m:m in [1..600000]|not 0 in Intseq(m) and IsSquare(8*m+1) and IsSquare(8*(&*Intseq(m))+1)]; // Marius A. Burtea, Aug 12 2019

Crossrefs

Cf. A000217, A002473, A007954.

Sequence in context: A270745 A137091 A137135 * A214838 A225789 A076551

Adjacent sequences: A069074 A069075 A069076 * A069078 A069079 A069080

Keyword

nonn,base

Author

Amarnath Murthy, Apr 05 2002

Extensions

More terms from Jason Earls and Lior Manor May 15 2002

Status

approved