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If n is the i-th positive integer with digital sum j, then a(n) is the j-th positive integer with digital sum i.
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%I #9 Oct 27 2015 21:22:48

%S 1,10,100,1000,10000,100000,1000000,10000000,100000000,2,11,20,101,

%T 110,200,1001,1010,1100,1000000000,12,21,30,102,111,120,201,210,2000,

%U 10000000000,22,31,40,103,112,121,130,300,10001,100000000000,32,41,50,104,113,122

%N If n is the i-th positive integer with digital sum j, then a(n) is the j-th positive integer with digital sum i.

%C Digital sum is given by A007953.

%C This is a self-inverse permutation of the natural numbers, with fixed points A081927.

%C A007953(n) = A081927(a(n)) for any n>0.

%C A081927(n) = A007953(a(n)) for any n>0.

%C a(A051885(n)) = 10^(n-1) for any n>0.

%C a(10^(n-1)) = A051885(n) for any n>0.

%H Paul Tek, <a href="/A263019/b263019.txt">Table of n, a(n) for n = 1..10000</a>

%H Paul Tek, <a href="/A263019/a263019.pl.txt">PERL program for this sequence</a>

%o (PARI) a(n) = {j = sumdigits(n); v = vector(n, k, sumdigits(k)); i = #select(x->x==j, v); nb = 0; k = 0; while(nb != j, k++; if (sumdigits(k) == i, nb++)); k;} \\ _Michel Marcus_, Oct 16 2015

%Y Cf. A007953, A051885, A081927, A254524, A263018.

%K nonn,base

%O 1,2

%A _Paul Tek_, Oct 07 2015