A354456 a(n) is the least number k such that k - 5^i is prime for i = 1..n.
7, 28, 132, 666, 3234, 17514, 100674, 501228, 2062662, 211097334, 2597411082, 34473310284, 214852200444, 394471192794
Offset: 1
Examples
a(3) = 132 because 132 - 5^1 = 127, 132 - 5^2 = 107 and 132 - 5^3 = 7 are all prime, and 132 is the least number with this property.
Programs
-
Maple
g:= proc(n) local p,x,i; p:= 1: do p:= nextprime(p); x:= p + 5^n; if andmap(isprime, [seq(x-5^i,i=1..n-1)]) then return x fi od end proc: map(g, [$1..10]); -
Python
from sympy import isprime, nextprime def a(n): p = 2 while True: k, p = 5**n + p, nextprime(p) if all(isprime(k-5**i) for i in range(1, n)): return k print([a(n) for n in range(1, 10)]) # Michael S. Branicky, May 30 2022
Extensions
a(11)-a(14) from David A. Corneth, May 30 2022
Comments