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A117822
a(0) = a(1) = 1; for n >= 2, a(n) = a(n-1) + a(n-2) - (n-1) if that number is positive and not already in the sequence, otherwise a(n) = a(n-1) + a(n-2) + (n-1).
3
1, 1, 3, 2, 8, 6, 9, 21, 23, 36, 50, 76, 115, 179, 281, 446, 712, 1142, 1837, 2961, 4779, 7720, 12478, 20176, 32631, 52783, 85389, 138146, 223508, 361626, 585105, 946701, 1531775, 2478444, 4010186, 6488596, 10498747, 16987307, 27486017, 44473286
OFFSET
0,3
MAPLE
a[0]:=1: a[1]:=1: A:={1}: for n from 2 to 42 do if a[n-1]+a[n-2]-(n-1)>0 and member(a[n-1]+a[n-2]-n+1, A)=false then a[n]:=a[n-1]+a[n-2]-n+1: A:=A union {a[n-1]+a[n-2]-n+1} else a[n]:=a[n-1]+a[n-2]+n-1: A:=A union {a[n-1]+a[n-2]+n-1} fi: od: seq(a[n], n=0..42); # Emeric Deutsch, Apr 30 2006
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Apr 30 2006
EXTENSIONS
More terms from Emeric Deutsch, Apr 30 2006
STATUS
approved