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 A335940 a(n) = n if n is prime, a(n) = 0 if n is a nontrivial power of a prime, and otherwise a(n) = max(|p-q| where p, q are distinct primes dividing n}. 1
 1, 2, 3, 0, 5, 1, 7, 0, 0, 3, 11, 1, 13, 5, 2, 0, 17, 1, 19, 3, 4, 9, 23, 1, 0, 11, 0, 5, 29, 3, 31, 0, 8, 15, 2, 1, 37, 17, 10, 3, 41, 5, 43, 9, 2, 21, 47, 1, 0, 3, 14, 11, 53, 1, 6, 5, 16, 27, 59, 3, 61, 29, 4, 0, 8, 9, 67, 15, 20, 5, 71, 1, 73, 35, 2, 17, 4, 11, 79, 3, 0, 39, 83 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) = A006530(n)-A020639(n) for n composite. - Chai Wah Wu, Jul 01 2020 EXAMPLE a(12) = 1 because its prime factors (2x2x3) have a maximum difference of 1 (3-2). a(14) = 5 because its prime factors (2x7) have a maximum difference of 5 (7-2). PROG (Python) import numpy as np def primeFactors(n):     x=[]     while n % 2 == 0:         x.append(2),         n = n / 2     for i in range(3, int(np.sqrt(n))+1, 2):         while n % i== 0:             x.append(i),             n = n / i     if n > 2:         x.append(n)     if len(x)==0:         x.append(1)     if len(x)!=1:         y=x[-1]-x     else:         y=x     return y     print(len(x)) nums = list(range(1, 101)) final=[] for i in nums:     final.append(primeFactors(i)) final = [int(i) for i in final] print(final) (Python) from sympy import primefactors, isprime def A335940(n):     if isprime(n):         return n     else:         pf = primefactors(n)         return max(pf)-min(pf) # Chai Wah Wu, Jul 01 2020 CROSSREFS Cf. A006530, A020639. Sequence in context: A066398 A138197 A140664 * A339767 A071321 A071322 Adjacent sequences:  A335937 A335938 A335939 * A335941 A335942 A335943 KEYWORD nonn AUTHOR Elam Blackwell, Jun 30 2020 STATUS approved

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Last modified August 9 21:08 EDT 2022. Contains 356026 sequences. (Running on oeis4.)