A050821 Even numbers in the sequence generated by a(n)=|a(n-1)+2a(n-2)-n| where a(0)=a(1)=1.

0, 2, 0, 6, 0, 2, 8, 6, 8, 10, 10, 8, 14, 0, 0, 26, 4, 18, 8, 14, 18, 20, 20, 18, 28, 14, 12, 26, 44, 14, 26, 24, 38, 16, 10, 32, 22, 32, 64, 10, 36, 38, 22, 36, 64, 10, 24, 14, 6, 24, 38, 44, 74, 28, 36, 50, 92, 14, 52, 50, 46, 56, 72, 38, 24, 106, 6, 68, 30, 0, 80, 58, 42, 20, 4

Offset

1,2

Links

Table of n, a(n) for n=1..75.

Mathematica

nxt[{n_, a_, b_}]:={n+1, b, Abs[b+2a-n-1]}; Select[NestList[nxt, {1, 1, 1}, 200][[All, 2]], EvenQ] (* Harvey P. Dale, Aug 25 2022 *)

Crossrefs

Cf. A005210.

Equals 2*A039727(n).

Sequence in context: A332400 A355143 A274878 * A076257 A274881 A303638

Adjacent sequences: A050818 A050819 A050820 * A050822 A050823 A050824

Keyword

nonn,easy

Author

Mohammad K. Azarian

Extensions

More terms from James A. Sellers

Definition clarified by Harvey P. Dale, Aug 25 2022

Status

approved