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A069077 Triangular numbers such that the product of digits is also a (positive) triangular number. 2
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 (list; graph; refs; listen; history; text; internal format)
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 *)

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

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Last modified November 13 00:25 EST 2019. Contains 329083 sequences. (Running on oeis4.)