A237189 - OEIS

%I #19 May 03 2021 20:15:22

%S 330,1530,3060,4260,4950,6840,10830,15390,18120,23010,25410,26040,

%T 31770,33300,40110,41490,45060,49830,53880,59340,65850,70140,73770,

%U 78540,88740,95460,96930,109470,111720,112620,117720,131310,133200,134730,135300,150150,165900

%N Numbers k such that k+1, 2k+1, 3k+1, 4k+1 are all prime.

%C A subsequence of A064238.

%C All terms are divisible by 30, and b(n)=a(n)/30 begins: 11, 51, 102, 142, 165, 228, 361, 513, 604, 767, 847, 868, 1059, 1110, 1337, 1383, 1502, 1661, 1796, 1978, 2195, ...

%H Jon E. Schoenfield, <a href="/A237189/b237189.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Giovanni Resta)

%F a(n) = 2*(A105653(n) + 1) = 2*A124409(n). - _Hugo Pfoertner_, May 03 2021

%o (Python)

%o import sympy

%o from sympy import isprime

%o for n in range(0,100000,2):

%o     if isprime(n+1) and isprime(2*n+1) and isprime(3*n+1) and isprime(4*n+1):

%o         print(str(n), end=',')

%Y Cf. A088250, A064238, A105653, A124409.

%K nonn

%O 1,1

%A _Alex Ratushnyak_, Feb 04 2014