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Let N = 1357911131517192123252729... = concatenation of odd numbers. Then a(n) = sum of first n digits of N.
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%I #6 Jul 09 2021 14:38:30

%S 1,4,9,16,25,26,27,28,31,32,37,38,45,46,55,57,58,60,63,65,70,72,79,81,

%T 90,93,94,97,100,103,108

%N Let N = 1357911131517192123252729... = concatenation of odd numbers. Then a(n) = sum of first n digits of N.

%H Harvey P. Dale, <a href="/A067115/b067115.txt">Table of n, a(n) for n = 1..1000</a>

%e a(6)= 1+3+5+7+9+1 = 26.

%t Module[{nn=20,codd},codd=Flatten[IntegerDigits/@(2Range[0,nn]+1)];Accumulate[ codd]] (* _Harvey P. Dale_, Jul 09 2021 *)

%Y Cf. A067112, A067113, A067114.

%K easy,nonn,base

%O 1,2

%A _Amarnath Murthy_, Jan 08 2002