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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
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
Sequence in context: A270745 A137091 A137135 * A214838 A225789 A076551
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 April 16 03:06 EDT 2024. Contains 371696 sequences. (Running on oeis4.)