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The sequence is a lattice filling using the exponential "E" constant digits base ten.
1

%I #13 Oct 04 2023 22:25:46

%S 1,21,371,8090,102125,1061609,12108836,198150335,1929504527

%N The sequence is a lattice filling using the exponential "E" constant digits base ten.

%t f[ 0 ] := 1; f[ n_Integer /; n > 0 ] := Module[ {i, cnt, m, p}, i = 0; cnt = 0; m = Table[ 0, {10^n} ]; p = Map[ FromDigits, Partition[ First[ RealDigits[ E, 10, 20*10^ n ] ], n, 1 ] ] + 1; Catch[ Map[ ( i++; If[ m[ [ # ] ] == 0, m[ [ # ] ] = 1; If[ ++cnt == 10^n, Throw[ i ] ] ]) &, p ] ] ];

%t Table[ f[ n ], {n, 0, 5} ]

%Y Cf. A001113.

%K nonn,uned,base

%O 0,2

%A _Roger L. Bagula_, Nov 28 2008, extended Nov 30 2008, Nov 30 2008

%E a(6)-a(8) from _Michael S. Branicky_, Oct 04 2023