OFFSET
1,2
COMMENTS
a(n) is the multiplicative order of 10 mod 9*(2n-1) if defined, otherwise 0.
MATHEMATICA
Table[s = MultiplicativeOrder[10, 9*(2*n - 1)]; If[! IntegerQ[s], 0, s], {n, 100}] (* T. D. Noe, Sep 20 2012 *)
PROG
(PARI) A216473(n)=if(n%5-3, znorder(Mod(10, 18*n-9))) \\ M. F. Hasler, Sep 29 2012
(PARI) for(i=0, 200, i++; if(i%5==0, print1(0", "), print1(znorder(Mod(10, 9*i))", "))) \\ V. Raman, Nov 22 2012
(PARI) for(i=0, 200, i++; m=0; for(x=1, i, if(((10^x-1)/9)%i==0, m=x; break)); print1(m", ")) \\ V. Raman, Nov 22 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
V. Raman, Sep 07 2012
EXTENSIONS
Definition corrected by V. Raman, Sep 20 2012
STATUS
approved