login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A278404 Greater number in the least prime-semiprime gap of size n. 2

%I #37 Nov 24 2016 12:06:11

%S 3,9,29,101,346,247,6098,3181,2878,2531,16033,26615,114371,41793,

%T 74506,39359,463178,104677,248426,517441,923743,506531,1930846,584237,

%U 2560202,4036993,4570438,4552391,7879282,4417843,27841082,5167619,13683067,9725141,47735377,25045807,63305698

%N Greater number in the least prime-semiprime gap of size n.

%C A prime-semiprime gap of n is defined as the difference between p & q, p being either a prime, A000040, or a semiprime, A001358, and q being the next greater prime or semiprime, see examples.

%C The corresponding numbers at the start of the prime-semiprime gaps, i.e., a(n)-n, are in A278351.

%H Bobby Jacobs, Charles R Greathouse IV, Jonathan Vos Post, and Robert G. Wilson v, <a href="/A278404/b278404.txt">Table of n, a(n) for n = 1..52</a>

%e a(1) = 3 since there is a gap of 1 between 2 and 3, both of which are primes.

%e a(2) = 9 since there is a gap of 2 between 7 and 9, the first is a prime and the second is a semiprime.

%e a(3) = 29 since there is a gap of 3 between 26, a semiprime, and 29, a prime.

%e a(6) = 247 because the first prime-semiprime gap of size 6 is between 241 and 247.

%Y Cf. A037143, A275013, A275014, A275108, A278351.

%K nonn

%O 1,1

%A _Bobby Jacobs_, _Charles R Greathouse IV_, _Jonathan Vos Post_, and _Robert G. Wilson v_, Nov 20 2016

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 3 12:40 EDT 2024. Contains 375670 sequences. (Running on oeis4.)