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A257533
Sum of the proper divisors of the n-th semiprime.
1
2, 5, 3, 7, 9, 8, 10, 13, 5, 15, 14, 19, 12, 21, 16, 25, 7, 20, 16, 22, 31, 33, 18, 26, 39, 18, 43, 22, 45, 32, 20, 34, 49, 24, 55, 40, 28, 61, 24, 11, 63, 44, 46, 26, 69, 50, 73, 24, 34, 75, 36, 81, 56, 30, 85, 13, 62, 91, 64, 42, 28, 99, 70
OFFSET
1,1
COMMENTS
For purposes of this sequence, the proper divisors of a number include all divisors other than 1 and the number itself. - Harvey P. Dale, Mar 15 2022
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A048050(A001358(n)).
A083681(n)-a(n) = A088707(n).
MAPLE
seq(A048050(A001358(n)), n=1..80) ;
MATHEMATICA
Total[Rest[Most[Divisors[#]]]]&/@Select[Range[250], PrimeOmega[#]==2&] (* Harvey P. Dale, Mar 15 2022 *)
PROG
(PARI) go(lim)=my(v=List()); forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), listput(v, [p*q, if(q<p, p+q, p)]))); v=vecsort(Vec(v), 1); apply(u->u[2], v) \\ Charles R Greathouse IV, Apr 28 2015
CROSSREFS
Cf. A083681.
Sequence in context: A135587 A191671 A176707 * A308021 A333201 A191707
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Apr 28 2015
STATUS
approved