A106649 - OEIS

%I #31 Jun 23 2024 08:04:34

%S 0,1,2,3,4,5,6,7,8,9,19,18,17,16,15,14,13,12,11,10,29,28,27,26,25,24,

%T 23,22,21,20,39,38,37,36,35,34,33,32,31,30,49,48,47,46,45,44,43,42,41,

%U 40,59,58,57,56,55,54,53,52,51,50,69,68,67,66,65,64,63,62,61,60,79,78,77

%N Replace each digit d (except the leading one) of n with 9-d.

%C By definition, one-digit numbers do not change.

%C Differs from A003100 starting with a(21)=29: A003100(21)=20.

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%F a(n) = n if n < 10, otherwise 10*a(floor(n/10)) + 9 - n mod 10; a self-inverse permutation of the natural numbers, A115310(n+8, 9) = a(n) for n > 0. - _Reinhard Zumkeller_, Jan 20 2006 [corrected by _Georg Fischer_, Jun 23 2024]

%F a(n) = A305238(n-9) for 10 <= n <= 99. - _M. F. Hasler_, Oct 16 2018

%t a[n_]:=FromDigits[Flatten[{IntegerDigits[n][[1]], Map[9-#&, Drop[IntegerDigits[n], 1]]}]];Table[a[n], {n, 0, 100}]

%Y Cf. A003100.

%Y Cf. A054429, A115303, A115304, A115305, A115306, A115307, A115308, A115309.

%K nonn,base

%O 0,3

%A _Zak Seidov_, May 12 2005