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%I #10 Jan 23 2022 13:53:48
%S 0,1,2,3,4,5,6,7,8,9,20,21,22,23,24,25,26,27,28,29,40,41,42,43,44,45,
%T 46,47,48,49,60,61,62,63,64,65,66,67,68,69,80,81,82,83,84,85,86,87,88,
%U 89,10,11,12,13,14,15,16,17,18,19,30,31,32,33,34,35,36
%N In decimal representation: replace each even positioned digit with the digit sum of its double.
%H Reinhard Zumkeller, <a href="/A249873/b249873.txt">Table of n, a(n) for n = 0..10000</a>
%H <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a>
%o (Haskell)
%o a249873 n = if n == 0 then 0 else 100*a249873 n' + 10*a007953 (2*t) + d
%o where (n', td) = divMod n 100; (t, d) = divMod td 10
%o (PARI) a(n) = my(d=Vecrev(digits(n))); forstep (i=2, #d, 2, d[i] = sumdigits(2*d[i])); fromdigits(Vecrev(d)); \\ _Michel Marcus_, Jan 23 2022
%Y Cf. A007953, A093017, A028897.
%K nonn,base
%O 0,3
%A _Reinhard Zumkeller_, Nov 08 2014
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