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Sum of digits of a(n) equals the sum of digits of 5*a(n).
3

%I #16 Sep 08 2022 08:46:13

%S 0,9,18,27,36,45,54,63,72,81,90,99,108,126,144,162,180,189,198,207,

%T 216,225,234,243,252,261,270,279,297,306,324,342,360,369,378,387,396,

%U 405,414,423,432,441,450,459,477,495,504,522,540,549,558,567,576,585,594

%N Sum of digits of a(n) equals the sum of digits of 5*a(n).

%C A007953(a(n)) = A007953(5*a(n)).

%C a(n) is a multiple of 9, but not all multiples of 9 belong to the sequence: 117 = 13*9: A007953(117) = 1 + 1 + 7 = 9, but A007953(5*117) = A007953(585) = 5 + 8 + 5 = 18.

%e 18 belongs to the sequence, because A007953(18) = 9 = A007953(90) = A007953(5*18).

%t Select[Range[0, 600], Total@ IntegerDigits@ # == Total@ IntegerDigits[5 #] &] (* _Michael De Vlieger_, Aug 05 2015 *)

%o (Magma) [n: n in [0..800] | &+Intseq(n) eq &+Intseq(5*n)]; // _Vincenzo Librandi_, Aug 05 2015

%Y Cf. A007953, A070279, A259727, A259728.

%K nonn,base

%O 1,2

%A _Christina Steffan_, Jul 05 2015