|
%I #27 Feb 12 2018 09:12:28
%S 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,
%T 16,49,53,39,32,25,75,7,42,20,45,65,16,63,22,31,107,33,40,62,18,77,57,
%U 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
%N Ch(n-th nonprime) where Ch(n) is Chowla's function, cf. A048050.
%C a(n) = A048050(A018252(n)).
%C a(n+1) = sum of nontrivial divisors of n-th composite number, or row sums in table A163870. - _Juri-Stepan Gerasimov_, Aug 06 2009
%H Reinhard Zumkeller, <a href="/A062825/b062825.txt">Table of n, a(n) for n = 1..10000</a>
%p 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
%t 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 *)
%o (PARI) j=[0]; for(n=2,200, if(isprime(n), n+1,j=concat(j, sigma(n)-n-1))); j
%o (Haskell)
%o a062825 1 = 0
%o a062825 n = sum $ a163870_row (n - 1) -- _Reinhard Zumkeller_, Mar 29 2014
%Y Cf. A048050, A002808.
%K nonn,look,easy
%O 1,2
%A _Jason Earls_, Jul 20 2001
%E Definition revised and a(1) corrected by _Reinhard Zumkeller_, Mar 29 2014
|
