%I A117823
%S A117823 0,1,3,7,6,8,20,21,33,45,68,102,158,247,391,623,998,1604,2584,4169,6733,
%T A117823 10881,17592,28450,46018,74443,120435,194851,315258,510080,825308,
%U A117823 1335357,2160633,3495957,5656556,9152478,14808998,23961439,38770399
%N A117823 a(0) = 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.
%p A117823 a[0]:=0: a[1]:=1: A:={0,1}: for n from 2 to 42 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..42); - Emeric Deutsch (deutsch(AT)duke.poly.edu), 
               Apr 30 2006
%Y A117823 Cf. A079053, A005132, A117821, A117822, A117824.
%Y A117823 Sequence in context: A021883 A075785 A105735 this_sequence A070882 A109635 
               A095360
%Y A117823 Adjacent sequences: A117820 A117821 A117822 this_sequence A117824 A117825 
               A117826
%K A117823 nonn,easy
%O A117823 0,3
%A A117823 N. J. A. Sloane (njas(AT)research.att.com), Apr 30 2006
%E A117823 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 30 2006