%I A117695
%S A117695 0,0,1,1,2,2,3,3,4,4,4,4,5,5,6,6,7,7,8,9,8,8,9,9,10,10,11,11,12,13,12,
%T A117695 12,13,13,14,14,15,15,16,18,16,16,17,17,18,18,19,19,20,22,20,20,21,21,
%U A117695 22,22,23,23,24,27,24,24,25,25,26,26,27,27,28,31,28,28,29,29,30,30,31
%N A117695 Number of different pairs of different numbers, with digits different 
               from zero, that produce a sum equal to 0, 1, 2, 3, 4, 5, 6, 7, 8, 
               etc.
%e A117695 Es. 10 = 1 + 9 = 2 + 8 = 3 + 7 = 4 + 6 therefore we have 4 different 
               couples
%e A117695 9 + 1 is not considered because is the same couple as 1 + 9
%e A117695 5 + 5 is not considered because we consider couples with different numbers
%p A117695 P:=proc(n)local i,j,k,cc,lm,ok,count; for cc from 1 by 1 to n do if trunc(cc/
               2)*2=cc then lm:=cc/2-1 else lm:=trunc(cc/2) fi; count:=0; for i 
               from 1 by 1 to lm do ok:=0; k:=i; while k>0 do j:=frac(k/10)*10; 
               if j=0 then ok:=1; fi; k:=trunc(k/10); od; k:=cc-i; while k>0 do 
               j:=frac(k/10)*10; if j=0 then ok:=1; fi; k:=trunc(k/10); od; if ok=1 
               then count:=count+1; fi; od; print(lm-count); od; end: P(1000);
%Y A117695 Cf. A117644.
%Y A117695 Sequence in context: A070549 A074796 A061070 this_sequence A074794 A048686 
               A090501
%Y A117695 Adjacent sequences: A117692 A117693 A117694 this_sequence A117696 A117697 
               A117698
%K A117695 nonn
%O A117695 0,5
%A A117695 Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Apr 13 2006