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!)
A340468 a(n) is the least prime of the form 2 + Product_{i=n..m} prime(i). 1
5, 7, 79, 13, 223, 19, 439, 130753887906569681111538991218568790437537693430279000532630035672131604633987039552816424896353327834998483765849409837393409377729040653460715050958787058270805333463, 31, 34826927179023475480751694965449235272424989980919 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

If n is in A029707, a(n) = 2+prime(n).

If n is not in A029707 but prime(n) is in A051507, a(n) = 2+prime(n)*prime(n+1).

a(15) > 10^1000 if it exists.

LINKS

Robert Israel, Table of n, a(n) for n = 2..14

EXAMPLE

a(2) = 2+3 = 5.

a(3) = 2+5 = 7.

a(4) = 2+7*11 = 79.

a(5) = 2+11 = 13.

a(6) = 2+13*17 = 223.

a(7) = 2+17 = 19.

a(8) = 2+19*23 = 439.

a(9) = 2+23*29*...*431.

MAPLE

f:= proc(n) local i, t;

t:= 1;

for i from n do

t:= t*ithprime(i);

if isprime(t+2) then return t+2 fi;

od

end proc:

seq(f(n), n=2..14);

PROG

(Python)

from sympy import isprime, nextprime, prime

def a(n):

prodpnpm = pm = prime(n)

while not isprime(2+prodpnpm): pm = nextprime(pm); prodpnpm *= pm

return 2+prodpnpm

print([a(n) for n in range(2, 12)]) # Michael S. Branicky, Jan 08 2021

CROSSREFS

Cf. A029707, A051507.

Sequence in context: A107140 A141746 A067198 * A351636 A062583 A196139

Adjacent sequences: A340465 A340466 A340467 * A340469 A340470 A340471

KEYWORD

nonn

AUTHOR

Robert Israel, Jan 08 2021

STATUS

approved

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 February 9 06:37 EST 2023. Contains 360153 sequences. (Running on oeis4.)