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).

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

Links

Table of n, a(n) for n=0..39.

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

Cf. A005132, A079053, A117821, A117823, A117824.

Sequence in context: A122358 A122297 A073283 * A132887 A364317 A092174

Adjacent sequences: A117819 A117820 A117821 * A117823 A117824 A117825

Keyword

nonn,easy

Author

N. J. A. Sloane, Apr 30 2006

Extensions

More terms from Emeric Deutsch, Apr 30 2006

Status

approved