login
A349659
Sum of the nonrefactorable divisors of n.
0
0, 0, 3, 4, 5, 9, 7, 4, 3, 15, 11, 13, 13, 21, 23, 20, 17, 9, 19, 39, 31, 33, 23, 13, 30, 39, 30, 53, 29, 69, 31, 52, 47, 51, 47, 13, 37, 57, 55, 39, 41, 93, 43, 81, 68, 69, 47, 77, 56, 90, 71, 95, 53, 90, 71, 53, 79, 87, 59, 93, 61, 93, 94, 116, 83, 141, 67, 123, 95, 141, 71
OFFSET
1,3
LINKS
Eric Weisstein's World of Mathematics, Refactorable Number
FORMULA
a(n) = A000203(n) - A335182(n).
a(p) = p for odd primes p. - Wesley Ivan Hurt, Nov 28 2021
MATHEMATICA
a[n_] := DivisorSum[n, # &, !Divisible[#, DivisorSigma[0, #]] &]; Array[a, 100] (* Amiram Eldar, Nov 24 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, if (d%numdiv(d), d)); \\ Michel Marcus, Nov 24 2021
CROSSREFS
Sequence in context: A215496 A122401 A122403 * A302653 A300738 A324506
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Nov 23 2021
STATUS
approved