A309571 Start with a(1)=1; thereafter the sequence is always extended by adding the n-th digit of the sequence to a(n) if both are of the same parity, otherwise subtracting it.

1, 2, 4, 8, 16, 15, 9, 10, 5, 14, 13, 13, 18, 17, 13, 14, 11, 12, 9, 10, 18, 17, 24, 23, 26, 25, 21, 22, 21, 22, 24, 15, 16, 16, 15, 7, 8, 1, -1, -5, -7, -4, -2, 4, 6, 1, -1, 0, 2, 4, 6, 5, 3, 1, -1, -5, -4, -9, -8, -2, -3, -9, -8, -13, -6, 2, 1, 2, -3, 4, 8, 10, 14, 20, 19, 20, 20

Offset

1,2

Links

Jean-Marc Falcoz, Table of n, a(n) for n = 1..42917

Example

The sequence S begins with 1,2,4,8,16,15,9,10,5,...
As a(1) = 1 and the 1st digit of S are of same parity, we get a(2) = 1 + 1 = 2;
as a(2) = 2 and the 2nd digit of S are of same parity, we get a(3) = 2 + 2 = 4;
as a(3) = 4 and the 3rd digit of S are of same parity, we get a(4) = 4 + 4 = 8;
as a(4) = 8 and the 4th digit of S are of same parity, we get a(5) = 8 + 8 = 16;
as a(5) = 16 and the 5th digit of S are not of same parity, we get a(6) = 16 - 1 = 15;
as a(6) = 15 and the 6th digit of S are not of same parity, we get a(7) = 15 - 6 = 9;
as a(7) = 8 and the 7th digit of S are of same parity, we get a(8) = 9 + 1 = 10.
Etc.

Crossrefs

This is a variant of A309529.

Sequence in context: A066005 A066600 A210025 * A210023 A301807 A062116

Adjacent sequences: A309568 A309569 A309570 * A309572 A309573 A309574

Keyword

sign,base

Author

Eric Angelini and Jean-Marc Falcoz, Aug 08 2019

Status

approved