A309529 Start with a(1)=2; thereafter the sequence is always extended by adding the n-th digit of the sequence to a(n) if a(n) is even, else subtracting it.

2, 4, 8, 16, 17, 11, 10, 17, 16, 17, 16, 16, 17, 10, 11, 5, 4, 11, 10, 16, 17, 11, 10, 17, 16, 16, 17, 16, 21, 17, 16, 17, 16, 16, 17, 11, 10, 17, 16, 17, 16, 16, 17, 10, 11, 5, 4, 10, 11, 4, 5, -1, -3, -4, -3, -10, -9, -15, -16, -9, -10, -4, -3, -9, -10

Offset

1,1

Comments

Among the first 10^8 terms, the last positive value occurs at n=28823742. - Lars Blomberg, Aug 10 2019

Links

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

Lars Blomberg, Graph of 10^8 terms

Lars Blomberg, Graph of accumulated sums of 10^8 terms

Example

The sequence begins with 2,4,8,16,17,11,10,17,...
As a(1) = 2 (even), we have a(2) = a(1) + [the 1st digit of the seq] = 2 + 2 = 4;
as a(2) = 4 (even), we have a(3) = a(2) + [the 2nd digit of the seq] = 4 + 4 = 8;
as a(3) = 8 (even), we have a(4) = a(3) + [the 3rd digit of the seq] = 8 + 8 = 16;
as a(4) = 16 (even), we have a(5) = a(4) + [the 4th digit of the seq] = 16 + 1 = 17;
as a(5) = 17 (odd), we have a(6) = a(5) - [the 5th digit of the seq] = 17 - 6 = 11;
as a(6) = 11 (odd), we have a(7) = a(6) - [the 6th digit of the seq] = 11 - 1 = 10;
etc.

Crossrefs

Cf. A309521 (same idea, but dealing with primes instead of even numbers).

Sequence in context: A008381 A083780 A368056 * A101466 A129851 A061681

Adjacent sequences: A309526 A309527 A309528 * A309530 A309531 A309532

Keyword

sign,base

Author

Eric Angelini and Jean-Marc Falcoz, Aug 06 2019

Status

approved