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A067991
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a(n) = k such that the k-th triangular number is A068808(n).
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0
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1, 2, 3, 7, 11, 12, 27, 31, 56, 107, 109, 132, 309, 343, 627, 968, 1332, 1891, 3129, 3434, 5291, 5656, 8831, 13332, 18972, 19492, 28248, 37067, 58309, 107516, 140547, 278172, 281743, 368507, 424256, 774325, 1247307, 2788547, 3126968, 3660565, 3949427, 7732916
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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EXAMPLE
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MAPLE
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dig := X->convert((convert(X, base, 10)), `+`); T := k->k*(k+1)/2; S := k->seq(dig(T(i)), i=1..k-1); seq(`if`(dig(T(i))>max(S(i)), i, printf("")), i=1..600);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Francois Jooste (phukraut(AT)hotmail.com), Mar 10 2002
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EXTENSIONS
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STATUS
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approved
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