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.

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, 12, 13, 13, 14, 14, 15, 15, 16, 18, 16, 16, 17, 17, 18, 18, 19, 19, 20, 22, 20, 20, 21, 21, 22, 22, 23, 23, 24, 27, 24, 24, 25, 25, 26, 26, 27, 27, 28, 31, 28, 28, 29, 29, 30, 30, 31

Offset

0,5

Links

Table of n, a(n) for n=0..76.

Example

Es. 10 = 1 + 9 = 2 + 8 = 3 + 7 = 4 + 6 therefore we have 4 different couples
9 + 1 is not considered because is the same couple as 1 + 9
5 + 5 is not considered because we consider couples with different numbers

Maple

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);

Crossrefs

Cf. A117644.

Sequence in context: A074796 A061070 A285879 * A074794 A234309 A306921

Adjacent sequences: A117692 A117693 A117694 * A117696 A117697 A117698

Keyword

nonn,base

Author

Paolo P. Lava and Giorgio Balzarotti, Apr 13 2006

Status

approved