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User:M. F. Hasler/Work in progress/Practical numbers

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Related sequences & pages:

  • A005153 Practical numbers: positive integers n such that every k <= sigma(n) is a sum of distinct divisors of n. Also called panarithmic numbers.
  • A007620 Numbers n such that every k <= n is a sum of proper divisors of n (for n>1). (subsequence of A005153)

Zhi-Wei Sun's sequences and conjectures:

  • Sandwiches:
    • A210479 List of primes p with p-1 and p+1 both practical.
  • Others: