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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
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 7 17:25 EST 2022. Contains 358668 sequences. (Running on oeis4.)