OFFSET
1,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = (c mod (c-1)) + (c mod (c-2)) + ... + (c mod 3) + (c mod 2).
EXAMPLE
a(1) = 1 (= (4 mod 3) + 0);
a(2) = 3 (= (6 mod 5) + (6 mod 4) + 0 + 0);
a(3) = 8 (= (8 mod 7) + (8 mod 6) + (8 mod 5) + 0 + (8 mod 3) + 0), etc.
MAPLE
A002808 := proc(n) local a; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; end if; end do; end if; end proc: A004125 := proc(n) add( n mod k, k=1..n) ; end: A161517 := proc(n) local c; A004125( A002808(n)) ; end: seq(A161517(n), n=1..80) ; # R. J. Mathar, Aug 03 2009
MATHEMATICA
With[{cmps=Select[Range[200], CompositeQ]}, Table[Total[Mod[n, Range[n-1]]], {n, cmps}]] (* Harvey P. Dale, Apr 09 2023 *)
PROG
(PARI) a(n)=my(c=n+n\log(n+1)); for(i=0, n-c+primepi(c), if(isprime(c++), i--)); sum(k=2, c, c%k) \\ Charles R Greathouse IV, Oct 12 2009
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Juri-Stepan Gerasimov, Jun 12 2009
EXTENSIONS
Corrected and extended by R. J. Mathar, Aug 03 2009
STATUS
approved