OFFSET
0,3
REFERENCES
N. J. A. Sloane, On single-deletion-correcting codes, in Codes and Designs (Columbus, OH, 2000), 273-291, Ohio State Univ. Math. Res. Inst. Publ., 10, de Gruyter, Berlin, 2002.
LINKS
N. J. A. Sloane, On single-deletion-correcting codes
N. J. A. Sloane, On single-deletion-correcting codes, 2002.
EXAMPLE
From Seiichi Manyama, Sep 02 2023: (Start)
1 + 2 == 3 mod 6,
3 == 3 mod 6,
1 + 3 + 5 == 3 mod 6,
2 + 3 + 4 == 3 mod 6,
4 + 5 == 3 mod 6,
1 + 2 + 3 + 4 + 5 == 3 mod 6.
So a(5) = 6. (End)
PROG
(PARI) a(n, k=3) = sumdiv(n+1, d, (d%2)*eulerphi(d)*moebius(d/gcd(d, k))/eulerphi(d/gcd(d, k))*2^((n+1)/d))/(2*(n+1)); \\ Seiichi Manyama, Sep 02 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 29 2000
EXTENSIONS
Offset changed to 0 by Seiichi Manyama, Sep 02 2023
STATUS
approved