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A117801
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Triangular numbers for which the product of the digits is a prime number.
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0
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OFFSET
| 1,1
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COMMENTS
| None of the digits can be 0,4,6,8 or 9. All the digits must be 1 or, just one digit can be 2,3,5 or 7 and all the others are 1.
There are no more terms less than 10^2580. - Hans Havermann (gladhobo(AT)teksavvy.com), May 07 2006
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EXAMPLE
| 1711 is in the sequence because (1)it is a triangular number and (2)the product of its digits is 1*7*1*1=7, which is a prime number.
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MATHEMATICA
| Select[Accumulate[Range[100000]], PrimeQ[Times@@IntegerDigits[#]]&] - from Harvey Dale, Dec 04 2010
Select[Table[n(n + 1)/2, {n, 10^3}], PrimeQ[Times@@IntegerDigits[#]]&] (* Zak Seidov, Dec 04 2010 *)
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CROSSREFS
| Cf. A000217.
Sequence in context: A171570 A076825 A118565 * A087674 A009057 A083795
Adjacent sequences: A117798 A117799 A117800 * A117802 A117803 A117804
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KEYWORD
| more,nonn,base
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AUTHOR
| Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006
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