A343375 a(n) is the least k such that Sum_{i=1..k} (i/prime(i))^n > 1.

2, 3, 6, 129, 107103, 19562634, 2433065908

Offset

1,1

Links

Table of n, a(n) for n=1..7.

Example

a(2)=3 because 3 terms are needed for a sum > 1:
(1/2)^2 + (2/3)^2 < 1, but (1/2)^2 + (2/3)^2 + (3/5)^2 > 1.
a(3)=6 because 6 terms are needed for a sum > 1:
(1/2)^3 + (2/3)^3 + (3/5)^3 + (4/7)^3 + (5/11)^3 + (6/13)^3 > 1.

Crossrefs

Cf. A000040.

Sequence in context: A018574 A018588 A018632 * A018646 A018665 A018673

Adjacent sequences: A343372 A343373 A343374 * A343376 A343377 A343378

Keyword

nonn,hard,more

Author

Alex Ratushnyak, Apr 12 2021

Extensions

a(7) from Daniel Suteu, May 04 2021

Status

approved