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A274790 Numbers in the range of the sum of odd divisors function. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 12 04:21 EST 2019. Contains 329051 sequences. (Running on oeis4.)