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Needs a b-file.
Table of n, a(n) for n=1..30.
Cf. A006561. Column k=2 of A292105.
Sequence in context: A301785 A066280 A192243 * A136113 A298992 A050189
Adjacent sequences: A292101 A292102 A292103 * A292105 A292106 A292107
N. J. A. Sloane, Sep 14 2017