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A218401
Triangular numbers composed of digits {0,7,9}.
2
990, 90779090007770790, 79909779970709079970099779979097777700
OFFSET
1,1
COMMENTS
a(4) > 10^40.
FORMULA
a(n) = A000217(A218402(n)).
CROSSREFS
Cf. A000217, A218402. See A119033 for a table of cross-references.
Sequence in context: A119095 A119077 A119057 * A053393 A365598 A031790
KEYWORD
base,nonn,more,hard,bref
AUTHOR
Max Alekseyev, Oct 28 2012
STATUS
approved