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 A334019 Sum of unitary divisors of n that are smaller than sqrt(n). 5
 0, 1, 1, 1, 1, 3, 1, 1, 1, 3, 1, 4, 1, 3, 4, 1, 1, 3, 1, 5, 4, 3, 1, 4, 1, 3, 1, 5, 1, 11, 1, 1, 4, 3, 6, 5, 1, 3, 4, 6, 1, 12, 1, 5, 6, 3, 1, 4, 1, 3, 4, 5, 1, 3, 6, 8, 4, 3, 1, 13, 1, 3, 8, 1, 6, 12, 1, 5, 4, 15, 1, 9, 1, 3, 4, 5, 8, 12, 1, 6, 1, 3, 1, 15, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS Jinyuan Wang, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A070039(n) for squarefree numbers (A005117) or squares of primes (A001248). EXAMPLE The unitary divisors of 12 are {1, 3, 4, 12}, 1 and 3 are smaller than sqrt(12) and their sum is 1 + 3 = 4, hence a(12) = 4. MATHEMATICA a[n_] := DivisorSum[n, # &, #^2 < n && CoprimeQ[#, n/#] &]; Array[a, 100] PROG (PARI) a(n) = sumdiv(n, d, if(gcd(d, n/d)==1 && d

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Last modified August 8 18:48 EDT 2024. Contains 375023 sequences. (Running on oeis4.)