A270392 - OEIS

%I #16 Nov 08 2016 21:03:41

%S 0,0,3,0,0,6,27,0,1,0,9,3,27,27,6,0,72,5,81,0,27,9,99,6,0,27,10,27,

%T 126,3,54,0,3,72,27,7,9,81,18,0,18,27,90,9,2,99,207,3,189,0,69,27,63,

%U 14,9,27,81,126,261,6,270,54,24,0,27,6,144,72,96,27,126,8,36,9,3,81,27,18,54,0,37,18,171,27,72,99,123,9

%N The sum of the digits in the periodic part of the decimal expansion of 1/n.

%C It appears that all nonzero terms in this sequence are divisible by 3 unless n is divisible by 9.

%F a(n) = A007953(A036275(n)).

%e 1/7 = 0.142857142857142857... and digit-cycle is 142857, the sum of these integers is 27 so a(7)=27.

%t a[n_] := Block[{d = RealDigits[1/n][[1,-1]]}, If[ IntegerQ@d, 0, Plus @@ d]]; Array[a, 100] (* _Giovanni Resta_, May 15 2016 *)

%Y Cf. A036275.

%K base,nonn,easy

%O 1,3

%A _Neville Styles_, Mar 16 2016