čtvrtek 30. srpna 2018

Puzzle 1: Sum of Powers of Primes

The whole story began around the turn of the millennium when Carlos Rivera  observed that 39 is a number with the following property:
(P1)     A non-prime number equal to the sum of consecutive primes from the least prime factor to the largest prime factor.
Of course, 39 = 3 * 13 = 3 + 5 + 7 + 11 + 13.
It is not difficult to verify that 10, 155 and 371 are other numbers with this property. Later (Jul. 2000), Jud McCranie found the 5th number:
2935561623745 = 5 * 19 * 53 * 61 * 9557877 = 5 + 7 + 11 + ... + 9557877.
On Nov. 2002, Robert Munafo discovered that
454539357304421 = 3536123 * 128541727 = 3536123 + 3536129 + 3536131 + ... + 128541727.
So, six numbers with the property (P1) are known up to now. One can find them in the Online Encyclopedia of Integer Sequences under the code A055233.
We change the property somewhat now:
(P2)     A non-prime-square number equal to the sum of squares of consecutive primes from the least prime factor to the largest prime factor.
The smallest number with this property is 315797.
Indeed,
315797 = 31 * 61 * 167 = 312 + 372 + 412 + ... + 1672.
Question A: Find other numbers with the property (P2).
We can continue.
(P3)     A non-prime-cube number equal to the sum of cubes of consecutive primes from the least prime factor to the largest prime factor.
In this case, there is a nice solution: 160.
160 = 25 * 5 = 23 + 33 + 53.
Question B: Find other numbers with the property (P3).
And finally:
Question C: The first, second and third powers of primes can be generalized to any n-th power. Find also any numbers for n>3.

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