The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A063845 a(n) = sigma(usigma(n)), where usigma(n) is the sum of unitary divisors of n (A034448) and sigma(n) is the sum of the divisors (A000203). 1
 1, 4, 7, 6, 12, 28, 15, 13, 18, 39, 28, 42, 24, 60, 60, 18, 39, 72, 42, 72, 63, 91, 60, 91, 42, 96, 56, 90, 72, 195, 63, 48, 124, 120, 124, 93, 60, 168, 120, 120, 96, 252, 84, 168, 168, 195, 124, 126, 93, 168, 195, 144, 120, 224, 195, 195, 186 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Harry J. Smith, Table of n, a(n) for n=1..1000 FORMULA a(n) = A000203(A034448(n)). - Michel Marcus, Dec 02 2015 MATHEMATICA usigma[n_] := DivisorSum[n, Boole[CoprimeQ[#, n/#]]*#& ]; a[n_] := DivisorSigma[1, usigma[n]]; Array[a, 60] (* Jean-François Alcover, Dec 02 2015 *) PROG (PARI) usigma(n) = sumdiv(n, d, if(gcd(d, n/d)==1, d)) { for (n=1, 1000, write("b063845.txt", n, " ", sigma(usigma(n))) ) } \\ Harry J. Smith, Sep 01 2009 CROSSREFS Sequence in context: A255248 A122460 A256659 * A188730 A019714 A021681 Adjacent sequences: A063842 A063843 A063844 * A063846 A063847 A063848 KEYWORD nonn AUTHOR N. J. A. Sloane, Oct 30 2001 STATUS approved

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 June 16 13:54 EDT 2024. Contains 373429 sequences. (Running on oeis4.)