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A218400
Numbers k such that the k-th triangular number contains only digits {0,4,7}.
2
284, 3080, 97680, 9460126854061817544
OFFSET
1,1
COMMENTS
No other terms below 1.4*10^20.
CROSSREFS
Cf. A000217, A218399. See A119034 for a table of cross-references.
Sequence in context: A143191 A180220 A108110 * A196893 A280808 A285892
KEYWORD
base,nonn,more
AUTHOR
Max Alekseyev, Oct 28 2012
STATUS
approved