A255678 - OEIS

%I #12 Jan 23 2022 12:46:09

%S 0,4,14,45,143,452,1431,4549,14334,46097

%N Smallest number m needing exactly n distinct digits in decimal representation of m*(m+1)/2.

%C A118668(a(n)) = n and A118668(m) <> n for m < a(n).

%o (Haskell)

%o a255678 n = head $ filter ((== n) . a118668) [0..]

%Y Cf. A118668, A260214 (the resulting triangular numbers).

%K nonn,base,fini,full

%O 1,2

%A _Reinhard Zumkeller_, Jul 11 2015