%I #6 Dec 05 2013 19:55:11
%S 9,91,1891,18915,1989015,199890015,19998900015,1999989000015,
%T 199999890000015,19999998900000015,1999999989000000015,
%U 199999999890000000015,19999999998900000000015
%N a(1) = 9; a(n+1) = smallest triangular number > a(n) formed by adding at least one digit to a(n).
%F For n>=4, a(n) = 2*10^(2n-4) - 11*10^(n-2) + 15 [From _Max Alekseyev_, Apr 25 2009]
%Y Cf. A068618, A068619, A068621, A068622, A068623.
%K base,more,nonn
%O 1,1
%A _Amarnath Murthy_, Feb 25 2002
%E 3 more terms from _Ray G. Opao_, Dec 09 2004
%E Extended by _Max Alekseyev_, Apr 25 2009
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