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%I #8 Feb 02 2023 17:02:06
%S 0,1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,0,2,3,4,5,6,7,8,9,0,1,3,4,5,6,
%T 7,8,9,0,1,2,4,5,6,7,8,9,0,1,2,3,5,6,7,8,9,0,1,2,3,4,6,7,8,9,0,1,2,3,
%U 4,5,7,8,9,0,1,2,3,4,5,6,8,9,0,1,2,3,4,5,6,7,9,0,1,2,3,4,5,6,7,8,1,2,3,4,5
%N Sum of digits of n modulo 10.
%F a(n) =A010879(A007953(n)) =(n+a(floor[n/10])) mod 10. So can construct sequence by starting with 0 and mapping 0->0123456789, 1->1234567890, 2->2345678901 etc. (e.g. 0, 0123456789, 0123456789123456789023456789013456789012456..., etc.) and looking at n-th digit of a term with sufficient digits.
%e a(59)=4 because 5+9 = 14 = 4 mod 10
%t Table[Mod[Total[IntegerDigits[n]],10],{n,0,120}] (* _Harvey P. Dale_, Oct 02 2018 *)
%o (PARI) a(n)=sumdigits(n)%10 \\ _Charles R Greathouse IV_, Feb 02 2023
%Y Cf. A000120, A007953, A010060, A053838-A053844.
%K base,nonn,easy
%O 0,3
%A _Henry Bottomley_, Mar 28 2000
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