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 A091921 Sum of odd proper distinct prime divisors of n. That is, the sum of odd distinct prime divisors of n that are less than n. 1
 0, 0, 0, 0, 0, 3, 0, 0, 3, 5, 0, 3, 0, 7, 8, 0, 0, 3, 0, 5, 10, 11, 0, 3, 5, 13, 3, 7, 0, 8, 0, 0, 14, 17, 12, 3, 0, 19, 16, 5, 0, 10, 0, 11, 8, 23, 0, 3, 7, 5, 20, 13, 0, 3, 16, 7, 22, 29, 0, 8, 0, 31, 10, 0, 18, 14, 0, 17, 26, 12, 0, 3, 0, 37, 8, 19, 18, 16, 0, 5, 3, 41, 0, 10, 22, 43, 32, 11, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA From Robert Israel, Jan 28 2018: (Start) If n is even, a(n) = A008472(n)-2. If n is prime, a(n) = A008472(n)-n = 0. Otherwise, a(n) = A008472(n). (End) EXAMPLE The sum of odd proper distinct prime divisors of 15 is 8=3+5. MAPLE seq(convert(numtheory:-factorset(n) minus {2, n}, `+`), n=1..100); # Robert Israel, Jan 28 2018 MATHEMATICA Table[Total[Select[Most[Divisors[n]], OddQ[#]&&PrimeQ[#]&]], {n, 90}] (* Harvey P. Dale, Dec 31 2023 *) PROG (PARI) a(n) = sumdiv(n, d, if ((d%2) && isprime(d) && (d

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Last modified June 14 15:00 EDT 2024. Contains 373400 sequences. (Running on oeis4.)