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A068623 a(1) = 8; a(n+1) = smallest triangular number > a(n) formed by adding at least one digit to a(n). 4

%I #6 Dec 05 2013 19:55:11

%S 8,28,528,18528,184528,18045028,1800450028,180004500028,

%T 18000045000028,1800000450000028,180000004500000028,

%U 18000000045000000028,1800000000450000000028,180000000004500000000028

%N a(1) = 8; a(n+1) = smallest triangular number > a(n) formed by adding at least one digit to a(n).

%F For n>=5, a(n) = 18*10^(2*n-6) + 45*10^(n-3) + 28 [From _Max Alekseyev_, Apr 25 2009]

%Y Cf. A068618, A068619, A068621, A068622, A068624.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Feb 25 2002

%E 3 more terms from _Ray G. Opao_, Dec 14 2004

%E Extended by _Max Alekseyev_, Apr 25 2009

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)