A117821 a(0) = a(1) = 1; for n >= 2, a(n) = a(n-1) + a(n-2) - n if that number is positive and not already in the sequence, otherwise a(n) = a(n-1) + a(n-2) + n.

1, 1, 4, 2, 10, 7, 11, 25, 28, 44, 62, 95, 145, 227, 358, 570, 912, 1465, 2359, 3805, 6144, 9928, 16050, 25955, 41981, 67911, 109866, 177750, 287588, 465309, 752867, 1218145, 1970980, 3189092, 5160038, 8349095, 13509097, 21858155, 35367214

Offset

0,3

Links

Table of n, a(n) for n=0..38.

Maple

a[0]:=1: a[1]:=1: A:={1}: for n from 2 to 40 do if a[n-1]+a[n-2]-n>0 and member(a[n-1]+a[n-2]-n, A)=false then a[n]:=a[n-1]+a[n-2]-n: A:=A union {a[n-1]+a[n-2]-n} else a[n]:=a[n-1]+a[n-2]+n: A:=A union {a[n-1]+a[n-2]+n} fi: od: seq(a[n], n=0..40); # Emeric Deutsch, Apr 30 2006

Crossrefs

Cf. A005132, A079053, A117822, A117823, A117824.

Sequence in context: A213584 A213587 A066579 * A266851 A185732 A121794

Adjacent sequences: A117818 A117819 A117820 * A117822 A117823 A117824

Keyword

nonn,easy

Author

N. J. A. Sloane, Apr 30 2006

Extensions

More terms from Benoit Cloitre and Emeric Deutsch, Apr 30 2006

Status

approved