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%I #9 Apr 17 2022 13:09:22
%S 0,2,4,6,8,10,12,14,16,18,2,4,6,8,10,12,14,16,18,20,4,6,8,10,12,14,16,
%T 18,20,22,6,8,10,12,14,16,18,20,22,24,8,10,12,14,16,18,20,22,24,26,10,
%U 12,14,16,18,20,22,24,26,28,12,14,16,18,20,22,24,26,28,30,14,16,18,20,22,24,26
%N Twice the sum of the digits of n.
%C The only n such that a(n) = n are 0 and 18.
%H Erich Friedman, <a href="https://erich-friedman.github.io/numbers.html">What's Special About This Number?</a>
%F a(n) = 2*A007953(n).
%t 2*Total[IntegerDigits[#]]&/@Range[0,80] (* _Harvey P. Dale_, Apr 17 2022 *)
%Y Cf. A007953.
%K nonn,base
%O 0,2
%A _N. J. A. Sloane_, May 24 2010
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