Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #16 Jan 25 2022 02:01:09
%S 2,3,6,129,107103,19562634,2433065908
%N a(n) is the least k such that Sum_{i=1..k} (i/prime(i))^n > 1.
%e a(2)=3 because 3 terms are needed for a sum > 1:
%e (1/2)^2 + (2/3)^2 < 1, but (1/2)^2 + (2/3)^2 + (3/5)^2 > 1.
%e a(3)=6 because 6 terms are needed for a sum > 1:
%e (1/2)^3 + (2/3)^3 + (3/5)^3 + (4/7)^3 + (5/11)^3 + (6/13)^3 > 1.
%Y Cf. A000040.
%K nonn,hard,more
%O 1,1
%A _Alex Ratushnyak_, Apr 12 2021
%E a(7) from _Daniel Suteu_, May 04 2021