The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A062825 Ch(n-th nonprime) where Ch(n) is Chowla's function, cf. A048050. 3
 0, 2, 5, 6, 3, 7, 15, 9, 8, 14, 20, 21, 10, 13, 35, 5, 15, 12, 27, 41, 30, 14, 19, 12, 54, 21, 16, 49, 53, 39, 32, 25, 75, 7, 42, 20, 45, 65, 16, 63, 22, 31, 107, 33, 40, 62, 18, 77, 57, 26, 73, 122, 39, 48, 63, 18, 89, 105, 39, 43, 139, 22, 45, 32, 91, 143, 20, 75, 34, 49, 24, 155, 72, 56, 116, 113, 105, 86, 55, 171, 105, 40, 135 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) = A048050(A018252(n)). a(n+1) = sum of nontrivial divisors of n-th composite number, or row sums in table A163870. - Juri-Stepan Gerasimov, Aug 06 2009 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 MAPLE with(numtheory): a_list := proc(n); {\$1..n} minus select(isprime, {\$1..n}); sort(convert(%, list)); map(f->add(d, d=(divisors(f) minus {1, f})), %) end: a_list(113); # Peter Luschny, Mar 29 2014 MATHEMATICA Reap[Do[If[!PrimeQ[k], Sow[If[k == 1, 0, DivisorSigma[1, k] - k - 1 ]]], {k, 1, 120}]][[2, 1]] (* Jean-François Alcover, Feb 12 2018 *) PROG (PARI) j=[0]; for(n=2, 200, if(isprime(n), n+1, j=concat(j, sigma(n)-n-1))); j (Haskell) a062825 1 = 0 a062825 n = sum \$ a163870_row (n - 1) -- Reinhard Zumkeller, Mar 29 2014 CROSSREFS Cf. A048050, A002808. Sequence in context: A336817 A340858 A309364 * A154925 A154962 A091655 Adjacent sequences:  A062822 A062823 A062824 * A062826 A062827 A062828 KEYWORD nonn,look,easy AUTHOR Jason Earls, Jul 20 2001 EXTENSIONS Definition revised and a(1) corrected by Reinhard Zumkeller, Mar 29 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 20 18:24 EDT 2021. Contains 345199 sequences. (Running on oeis4.)