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a(0) = 0; a(n) = DecimalDigitsSortedDecreasing(a(n-1) + 1) for n > 0.
4

%I #29 Aug 08 2023 23:33:02

%S 0,1,2,3,4,5,6,7,8,9,10,11,21,22,32,33,43,44,54,55,65,66,76,77,87,88,

%T 98,99,100,110,111,211,221,222,322,332,333,433,443,444,544,554,555,

%U 655,665,666,766,776,777,877,887,888,988,998,999,1000,1100,1110,1111,2111

%N a(0) = 0; a(n) = DecimalDigitsSortedDecreasing(a(n-1) + 1) for n > 0.

%C a(n) = A004186(a(n-1) + 1). - _Reinhard Zumkeller_, Oct 31 2007

%H Reinhard Zumkeller, <a href="/A064222/b064222.txt">Table of n, a(n) for n = 0..1000</a>

%F a(n+1) = (d+0^d)*10^floor(log_10(a(n)+1)) + (1-0^d)*floor(a(n)/10), where d = (a(n)+1) mod 10. - _Reinhard Zumkeller_, Oct 31 2007

%F a(n) = (ceiling( (n-G(D(n)-1))/D(n) )*(10^D(n) -1) - 10^( (G(D(n)-1)-n) mod (D(n)) ) + 1)/9, for n>0, where D(n) = floor( (sqrt(8n+1)+3)/6 ) is the number of digits in a(n), and G(k) = A027468(k) = 9*k*(k+1)/2. - _Stefan Alexandru Avram_, May 24 2023

%t NestList[FromDigits[Sort[IntegerDigits[#+1],Greater]]&,0,60] (* _Harvey P. Dale_, Sep 04 2011 *)

%o (Haskell)

%o a064222 n = a064222_list !! n

%o a064222_list = iterate (a004186 . (+ 1)) 0

%o -- _Reinhard Zumkeller_, Apr 11 2012

%Y Cf. A004186, A004216, A027468.

%K nice,nonn,base,look

%O 0,3

%A _Reinhard Zumkeller_, Sep 21 2001