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 A117695 a(n) is the number of pairs of distinct positive integers not containing a digit 0 giving a sum equal to n. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS David A. Corneth, Table of n, a(n) for n = 1..10000 EXAMPLE 10 = 1 + 9 = 2 + 8 = 3 + 7 = 4 + 6 therefore we have 4 different couples. 9 + 1 is not considered because it 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); PROG (PARI) iszerofree(n) = vecmin(digits(n)) > 0 a(n) = sum(i = 1, (n-1)\2, iszerofree(i) && iszerofree(n-i)) \\ David A. Corneth, May 12 2024 CROSSREFS Cf. A117644. Sequence in context: A074796 A061070 A285879 * A074794 A234309 A306921 Adjacent sequences: A117692 A117693 A117694 * A117696 A117697 A117698 KEYWORD nonn,base,changed AUTHOR Paolo P. Lava and Giorgio Balzarotti, Apr 13 2006 EXTENSIONS Name edited and offset changed to 1 by David A. Corneth, May 12 2024 STATUS approved

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Last modified May 19 03:29 EDT 2024. Contains 372666 sequences. (Running on oeis4.)