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A274790
Numbers in the range of the sum of odd divisors function.
4
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
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
KEYWORD
nonn
AUTHOR
Timothy L. Tiffin, Jul 06 2016
STATUS
approved