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A163505
a(n) = (n-th odd nonprime) mod (n-th odd number).
1
0, 0, 0, 0, 7, 5, 7, 5, 5, 7, 7, 5, 5, 3, 5, 3, 3, 5, 3, 3, 3, 1, 1, 46, 46, 48, 52, 1, 1, 58, 58, 58, 58, 58, 60, 62, 62, 66, 66, 66, 66, 70, 70, 72, 72, 74, 76, 76, 78, 78, 82, 82, 82, 82, 86, 90, 90, 90, 90, 90, 92, 92, 92, 92, 92, 94, 98, 100, 100, 104, 104, 104, 104, 106, 106
OFFSET
1,5
LINKS
FORMULA
a(n) = A014076(n) mod A005408(n-1). [corrected by R. J. Mathar, Oct 10 2009]
EXAMPLE
a(1) = 1 mod 1 = 0;
a(2) = 9 mod 3 = 0;
a(3) = 15 mod 5 = 0;
a(4) = 21 mod 7 = 0;
a(5) = 25 mod 9 = 7.
MAPLE
A014076 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then return a; end if; end do: end if; end proc:
A163505 := proc(n) A014076(n) mod (2*n-1); end: seq(A163505(n), n=1..80) ; # R. J. Mathar, Oct 10 2009
MATHEMATICA
A014076 := Select[Range[1, 10000, 2], PrimeOmega[#] != 1 &]; Table[Mod[A014076[[n]], 2*n - 1], {n, 1, 50}] (* G. C. Greubel, Jul 27 2017 *)
CROSSREFS
Sequence in context: A021573 A080411 A178988 * A021136 A214444 A194657
KEYWORD
nonn
AUTHOR
EXTENSIONS
Missing term between a(53) and a(54) inserted by G. C. Greubel, Jul 27 2017
STATUS
approved