A274790 Numbers in the range of the sum of odd divisors function.

1, 4, 6, 8, 12, 13, 14, 18, 20, 24, 30, 31, 32, 38, 40, 42, 44, 48, 54, 56, 57, 60, 62, 68, 72, 74, 78, 80, 84, 90, 96, 98, 102, 104, 108, 110, 112, 114, 120, 121, 124, 128, 132, 133, 138, 140, 144, 150, 152, 156, 158, 160, 164, 168, 174, 176, 180, 182, 183

Offset

1,2

Comments

Numbers which appear in A000593.

Possible values for the sum of odd divisors of the positive integers, in increasing order. - Omar E. Pol, Jul 06 2016

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

N:= 10000:# to get all terms <= N
p:= 3:
S:= {1}:
while p < N do
  S:= map(s -> seq(s*(p^(e+1)-1)/(p-1), e=0..ilog[p](1+N*(p-1)/s)-1), S);
  p:= nextprime(p);
od:
sort(convert(S, list)); # Robert Israel, Jul 06 2016

Mathematica

Union@ Table[Total@ Select[Divisors@ n, OddQ], {n, 200}] (* Michael De Vlieger, Jul 07 2016 *)

Prog

(PARI) list(lim)=lim\=1; my(v=[1]); forprime(p=3, lim\4, my(t, u=v, lm); for(e=1, logint(lim, p), t=(p^(e+1)-1)/(p-1); lm=lim\t; u=concat(u, select(k->k<=lm, v)*t)); v=Set(u)); Set(concat(v, apply(p->p+1, primes([lim\4, lim-1])))) \\ Charles R Greathouse IV, Jul 06 2016

Crossrefs

Cf. A000593, subsequence of A002191, A274793 (complement).

Sequence in context: A234520 A275789 A031359 * A179852 A281020 A110606

Adjacent sequences: A274787 A274788 A274789 * A274791 A274792 A274793

Keyword

nonn

Author

Timothy L. Tiffin, Jul 06 2016

Status

approved