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%I #20 May 02 2023 11:25:35
%S 1,3,5,7,9,11,13,15,17,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,
%T 80,84,88,92,96,100,104,108,112,116,120,124,128,132,136,140,144,148,
%U 152,156,160,164,168,172,176,180,184,188,192,196,200,204,208,212,216,220,224,228,232
%N a(n) is the number of decimal digits in A173426(n).
%F a(n) = A058183(n) + A058183(n-1), for n >= 2.
%F a(n) = A055642(A173426(n)).
%F a(n) = 2*A058183(n) - A055642(n).
%e a(12)=28 since 1234567891011121110987654321 has 28 digits.
%o (PARI)
%o a(n)={my(t=logint(n,10)+1); 2*n*t-2*(10^t-1)/9+t}
%o (Python)
%o def a(n): return ((n*(t:=len(str(n)))-(10**t-1)//9)<<1) + t
%o print([a(n) for n in range(1, 64)]) # _Michael S. Branicky_, May 02 2023
%Y Cf. A173426, A058183, A055642.
%K nonn,base
%O 1,2
%A _David Cleaver_, Apr 29 2023