The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A110412 Sum_{d
 0, 1, 2, 4, 3, 7, 4, 9, 8, 9, 4, 17, 6, 10, 14, 18, 5, 20, 6, 21, 16, 12, 4, 33, 14, 13, 18, 24, 6, 33, 8, 29, 18, 12, 18, 44, 9, 13, 17, 41, 8, 37, 8, 26, 39, 14, 4, 57, 18, 30, 20, 28, 6, 41, 20, 45, 20, 14, 4, 68, 12, 16, 40, 46, 25, 43, 8, 25, 18, 44, 8, 80, 12, 16, 42, 30, 22, 42, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Table of n, a(n) for n=1..79. FORMULA It appears that a(n) > tau(n) for n >= 4. EXAMPLE a(9) = tau(9-1)+tau(9-3) = tau(8)+tau(6) = 4+4 = 8. MAPLE with(numtheory): a:=proc(n) local div: div:=divisors(n): sum(tau(n-div[j]), j=1..tau(n)-1): end: seq(a(n), n=2..90); # Emeric Deutsch, Aug 05 2005 MATHEMATICA f[n_] := Plus @@ (DivisorSigma[0, n - # ] & /@ Most[Divisors[n]]); Table[ f[n], {n, 79}] (* Robert G. Wilson v, Aug 05 2005 *) PROG (PARI) a(n) = sumdiv(n, d, if (d

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.

Last modified April 21 00:22 EDT 2024. Contains 371850 sequences. (Running on oeis4.)