|
%I #17 Dec 21 2023 15:03:43
%S 1,5,11,71,863,10427,42571,95569,2145089,42997349,1292065559,
%T 12963652939,27219371437,285157367309,6870996186853,261383012467723,
%U 10984957519831219,922997814678290119,27700919397868534789,333334030589100707587,3361041225288875610659
%N a(1) = 1, a(2) = 5, for n >= 3, a(n) = smallest prime > a(n-1) such that a(n) mod a(n-1) = a(n-2).
%C a(389) has 1002 digits. - _Michael S. Branicky_, Dec 21 2023
%H Michael S. Branicky, <a href="/A175207/b175207.txt">Table of n, a(n) for n = 1..388</a>
%t nmax= 11; a[1]=1; a[2]=5; kmin=1; For[n=3, n<=nmax, n++, For[k=kmin, k>0, k++, If[Mod[Prime[k],a[n-1]]==a[n-2], a[n]=Prime[k]; kmin=k; k=-1]]]; Array[a,nmax] (* _Stefano Spezia_, Sep 16 2022 *)
%o (Python)
%o from gmpy2 import is_prime
%o from itertools import count, islice
%o def agen(): # generator of terms
%o c, b = 1, 5
%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(), 22))) # _Michael S. Branicky_, Dec 21 2023
%Y Cf. A175093, A175094, A175208.
%K nonn
%O 1,2
%A _Jaroslav Krizek_, Mar 04 2010
%E Definition corrected by _Stefano Spezia_, Sep 16 2022
%E a(12) and beyond from _Michael S. Branicky_, Dec 21 2023
|
