A309216 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.

0, 1, -1, -4, 0, 5, -1, -8, 0, 9, -1, -12, -24, -11, 3, 18, 2, -15, -33, -52, -32, -11, -33, -56, -80, -105, -131, -104, -132, -103, -133, -164, -196, -229, -263, -228, -192, -155, -193, -154, -194, -235, -277, -320, -364, -319, -273, -320, -368, -319, -369, -318, -370, -423, -477, -532

Offset

0,4

Comments

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.)

Links

N. J. A. Sloane, Table of n, a(n) for n = 0..10000

Maple

t:=0;
a:=[0]; b:=[]; M:=100;
for i from 1 to M do
v1:=convert(abs(t), base, 10); L:=nops(v1);
v2:=[seq(v1[L-i+1], i=1..L)];
b:=[op(b), op(v2)];
if (b[i] mod 2) = 0 then t:=t+i else t:=t-i; fi;
a:=[op(a), t];
od:
a;

Crossrefs

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

Sequence in context: A003816 A309214 A309215 * A083745 A327545 A306072

Adjacent sequences: A309213 A309214 A309215 * A309217 A309218 A309219

Keyword

sign,base

Author

N. J. A. Sloane, Aug 10 2019

Status

approved