A309216 - OEIS

%I #12 Aug 10 2019 15:54:29

%S 0,1,-1,-4,0,5,-1,-8,0,9,-1,-12,-24,-11,3,18,2,-15,-33,-52,-32,-11,

%T -33,-56,-80,-105,-131,-104,-132,-103,-133,-164,-196,-229,-263,-228,

%U -192,-155,-193,-154,-194,-235,-277,-320,-364,-319,-273,-320,-368,-319,-369,-318,-370,-423,-477,-532

%N a(0)=0; thereafter a(n) = a(n-1)+n if the (n-1)st digit of the sequence is even, otherwise a(n) = a(n-1)-n.

%C The absolute values of the digits are 0, 1, 1, 4, 0, 5, 1, 8, 0, 9, 1, 1, 2, 2, 4, 1, 1, 3, 1, 8, 2, 1, 5, 3, 3, 5, 2, ... (Of course the signs can be ignored when looking at the parity of the digits.)

%H N. J. A. Sloane, <a href="/A309216/b309216.txt">Table of n, a(n) for n = 0..10000</a>

%p t:=0;

%p a:=[0]; b:=[]; M:=100;

%p for i from 1 to M do

%p v1:=convert(abs(t),base,10); L:=nops(v1);

%p v2:=[seq(v1[L-i+1],i=1..L)];

%p b:=[op(b),op(v2)];

%p if (b[i] mod 2) = 0 then t:=t+i else t:=t-i; fi;

%p a:=[op(a),t];

%p od:

%p a;

%Y Cf. A003816, A309529, A309214, A309215, A309217.

%K sign,base

%O 0,4

%A _N. J. A. Sloane_, Aug 10 2019