A117824 a(0) = 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).

0, 1, 2, 5, 4, 13, 12, 19, 24, 35, 50, 75, 114, 177, 278, 441, 704, 1129, 1816, 2927, 4724, 7631, 12334, 19943, 32254, 52173, 84402, 136549, 220924, 357445, 578340, 935755, 1514064, 2449787, 3963818, 6413571, 10377354, 16790889, 27168206, 43959057

Offset: 0

Author

N. J. A. Sloane, Apr 30 2006

Keywords

• nonn
• easy

Crossrefs

Cf. A005132, A079053, A117821, A117822, A117823.

Programs

Maple

a[0]:=0: a[1]:=1: A:={0,1}: 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

Extensions

More terms from Emeric Deutsch, Apr 30 2006