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A119040
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Numbers k such that the k-th triangular number contains only digits {0,1,5}.
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2
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1, 4, 5, 10, 14, 100, 101, 141, 173, 458, 1000, 1001, 1005, 1010, 4475, 10000, 10001, 10005, 10010, 10100, 10110, 10114, 14869, 45858, 54873, 100000, 100001, 100005, 100010, 100100, 100101, 101000, 101005, 1000000, 1000001, 1000005, 1000010
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[2 10^6], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 5}] == {} &] (* Vincenzo Librandi, Dec 25 2015 *)
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PROG
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(Magma) [n: n in [1..2*10^6] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 5]]; // Vincenzo Librandi, Dec 25 2015
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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