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[ Even numbers in the sequence generated by b(n)=|b(n-1)+2b(n-2)-n| ], divided by 2.
1

%I #10 Oct 24 2018 22:37:05

%S 0,0,1,0,3,0,1,4,3,4,5,5,4,7,0,0,13,2,9,4,7,9,10,10,9,14,7,6,13,22,7,

%T 13,12,19,8,5,16,11,16,32,5,18,19,11,18,32,5,12,7,3,12,19,22,37,14,18,

%U 25,46,7,26,25,23,28,36,19,12,53,3,34,15,0,40,29,21,10,2,9,54,15,14,57,35

%N [ Even numbers in the sequence generated by b(n)=|b(n-1)+2b(n-2)-n| ], divided by 2.

%t Select[RecurrenceTable[{a[0]==0,a[1]==1,a[n]==Abs[a[n-1]+2a[n-2]-n]},a,{n,200}],EvenQ]/2 (* _Harvey P. Dale_, Oct 24 2018 *)

%Y Equals A050821/2.

%K easy,nonn

%O 1,5

%A _James A. Sellers_

%E Zero prepended by _Harvey P. Dale_, Oct 24 2018