cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A370305 Numbers k such that the distance from exp(k) to the closest average of two consecutive primes is less than 1.

This page as a plain text file.
%I A370305 #8 Feb 16 2024 14:56:38
%S A370305 1,3,16,61,74,91,113,1441,1566,2170,2499
%N A370305 Numbers k such that the distance from exp(k) to the closest average of two consecutive primes is less than 1.
%C A370305 Explicitly, abs( e^k - (prevprime(e^k)+nextprime(e^k))/2 ) < 1.
%C A370305 For k>1, the formula (prevprime(e^k)+nextprime(e^k))/2 either gives floor(e^k), for k = 61, 74, 2170, ..., or gives ceiling(e^k), for k = 3, 16, 91, 113, 1441, 1566, 2499, ... This partitions {a(n)}\{1} into two subsequences each of which can be conjectured to have relative density 1/2.
%C A370305 In cases k = 16, 61, 113, 2499, ... the distance is actually less than 0.5. Then the formula (prevprime(e^k)+nextprime(e^k))/2 yields round(e^k), the nearest integer to e^k.
%e A370305 For k=16, e^16 is about 8886110.52. The next prime is 8886113, and the previous prime is 8886109, and their average 8886111 is at a distance of about 0.48 away from e^16.
%o A370305 (PARI) default(realprecision,2000);for(k=1,+oo,r=exp(k);abs(r-(precprime(r)+nextprime(r))/2)<1&&print1(k,", "))
%Y A370305 Cf. A037028, A040016, A050808, A059303, A074496.
%K A370305 nonn,hard,more
%O A370305 1,2
%A A370305 _Jeppe Stig Nielsen_, Feb 14 2024