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!)
A175208 a(1) = 1, a(2) = 7, for n >= 3, a(n) = smallest prime > a(n-1) such that a(n) mod a(n-1) = a(n-2). 3

%I #19 Dec 21 2023 15:04:08

%S 1,7,29,181,4373,61403,2583299,41394187,85371673,895110917,

%T 16197368179,98079319991,800831928107,3301407032419,159268369484219,

%U 5736962708464303,46054970037198643,4703343906502725889,18859430596048102199,155578788674887543481,4375065513492899319667

%N a(1) = 1, a(2) = 7, for n >= 3, a(n) = smallest prime > a(n-1) such that a(n) mod a(n-1) = a(n-2).

%C It appears that the definition should include the condition that the sequence is strictly increasing - true? - _N. J. A. Sloane_, Jan 27 2019

%C a(390) has 1002 digits. - _Michael S. Branicky_, Dec 21 2023

%H Michael S. Branicky, <a href="/A175208/b175208.txt">Table of n, a(n) for n = 1..389</a> (terms 1..33 from Charlie Neder)

%o (Python)

%o from gmpy2 import is_prime

%o from itertools import count, islice

%o def agen(): # generator of terms

%o c, b = 1, 7

%o yield from [c, b]

%o for n in count(3):

%o a = next(c + b*i for i in count(1) if is_prime(c+b*i))

%o c, b = b, a

%o yield a

%o print(list(islice(agen(), 21))) # _Michael S. Branicky_, Dec 21 2023

%Y Cf. A175093, A175094, A175207.

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Mar 04 2010

%E a(12)-a(20) from _Charlie Neder_, Jan 25 2019

%E Name corrected per _N. J. A. Sloane_'s comment by _Michael S. Branicky_, Dec 21 2023

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 March 29 08:01 EDT 2024. Contains 371265 sequences. (Running on oeis4.)