OFFSET
1,2
COMMENTS
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
KEYWORD
AUTHOR
Jason Earls, Jul 20 2001
EXTENSIONS
Definition revised and a(1) corrected by Reinhard Zumkeller, Mar 29 2014
STATUS
approved