A158962 a(n) is the smallest number m such that all n numbers m-1, m.m-1, ..., m.m. .. .m-1 are prime, where dot means concatenation.
3, 4, 4, 444, 827868, 10387692, 1885781034
Offset: 1
Examples
All 4 numbers 444-1,444444-1,1+444444444-1,444444444444-1 are prime and 444 is the smallest such number so a(4)=444.
Crossrefs
Cf. A153434.
Programs
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Maple
a:= proc(n) local m; for m do if andmap(isprime, [seq(parse(cat(m$i))-1, i=1..n)]) then return m fi od end: seq(a(n), n=1..5); # Alois P. Heinz, Apr 14 2021 -
Python
from sympy import isprime def A158962(n): m = 1 while True: for i in range(n): if not isprime(int(str(m)*(i+1))-1): break else: return m m += 1 # Chai Wah Wu, Apr 14 2021