The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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
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
KEYWORD
nonn,base,changed
AUTHOR
EXTENSIONS
Name edited and offset changed to 1 by David A. Corneth, May 12 2024
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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