cp's OEIS Frontend

A076068 Smallest number that can be formed by using the nonzero digits of the numbers 1+n(n-1)/2 through n(n+1)/2.

%I A076068 #16 Jan 23 2021 10:02:37
%S A076068 1,23,456,1789,1111112345,11111226789,22222222345678,122333333334569,
%T A076068 12333344444445789,1234444455555556789,123455555666666666789,
%U A076068 12345666677777777777889,112345677888888888889999,111111122334455678999999999,111111111111111111111111112234566778899
%N A076068 Smallest number that can be formed by using the nonzero digits of the numbers 1+n(n-1)/2 through n(n+1)/2.
%C A076068 Is there any r and s such that a(r) = a(s)? Probably not.
%e A076068 a(4) = 1789 (=01789) formed by using digits of 7,8,9 and 10.
%t A076068 sncbf[n_]:=Sort[Flatten[IntegerDigits/@Range[(n(n-1))/2+1,(n(n+1))/2]]/.(0->Nothing)]//FromDigits; Array[sncbf,15] (* _Harvey P. Dale_, Nov 26 2019 *)
%o A076068 (Python)
%o A076068 def a(n):
%o A076068   s = "".join(sorted("".join(map(str, range((n-1)*n//2+1, n*(n+1)//2+1)))))
%o A076068   if '0' not in s: return int(s)
%o A076068   return int(s[s.rfind('0')+1:])
%o A076068 print([a(n) for n in range(1, 16)]) # _Michael S. Branicky_, Jan 23 2021
%Y A076068 Cf. A053067 (next n concatenated), A080479 (smallest with zeros), A080480 (largest with zeros).
%K A076068 base,easy,nonn
%O A076068 1,2
%A A076068 _Amarnath Murthy_, Oct 05 2002
%E A076068 More terms from _David Wasserman_, Mar 19 2005