cp's OEIS Frontend

A243861 Primes p for which p^i - 4 is prime for i = 1, 3, 5 and 7.

%I A243861 #11 May 22 2025 10:21:38
%S A243861 971,12641,205607,228341,276557,412343,1012217,1101323,1902881,
%T A243861 2171021,2477411,2692121,4116377,4311677,6060953,6182993,6388913,
%U A243861 6444863,8341121,8551451,9507527,10523141,10997411,11444093,14101361,14656307,14813147,15435587,17337521
%N A243861 Primes p for which p^i - 4 is prime for i = 1, 3, 5 and 7.
%C A243861 Subsequence of A243818: Primes p for which p^i - 4 is prime for i = 1, 3 and 5.
%H A243861 Abhiram R Devesh, <a href="/A243861/b243861.txt">Table of n, a(n) for n = 1..100</a>
%e A243861 Prime p=971 is in this sequence because p-4 = 967 (prime), p^3-4 = 915498607 (prime),  p^5-4 = 863169625893847 (prime), and p^7-4 = 813831713247384370687 (prime).
%o A243861 (Python)
%o A243861 import sympy.ntheory as snt
%o A243861 n=2
%o A243861 while n>1:
%o A243861     n1=n-4
%o A243861     n2=((n**3)-4)
%o A243861     n3=((n**5)-4)
%o A243861     n4=((n**7)-4)
%o A243861     ##Check if n1 , n2, n3 and n4 are also primes.
%o A243861     if snt.isprime(n1)== True and snt.isprime(n2)== True and snt.isprime(n3)== True and snt.isprime(n4)== True:
%o A243861         print(n, n1, n2, n3, n4)
%o A243861     n=snt.nextprime(n)
%Y A243861 Cf. A023200, A243583, A243780, A243818.
%K A243861 nonn,easy
%O A243861 1,1
%A A243861 _Abhiram R Devesh_, Jun 12 2014