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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. 7
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 (list; graph; refs; listen; history; text; internal format)
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: A316749 A008381 A083780 * 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

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Last modified September 30 11:32 EDT 2020. Contains 337439 sequences. (Running on oeis4.)