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A237189
Numbers k such that k+1, 2k+1, 3k+1, 4k+1 are all prime.
4
330, 1530, 3060, 4260, 4950, 6840, 10830, 15390, 18120, 23010, 25410, 26040, 31770, 33300, 40110, 41490, 45060, 49830, 53880, 59340, 65850, 70140, 73770, 78540, 88740, 95460, 96930, 109470, 111720, 112620, 117720, 131310, 133200, 134730, 135300, 150150, 165900
OFFSET
1,1
COMMENTS
A subsequence of A064238.
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, ...
LINKS
Jon E. Schoenfield, Table of n, a(n) for n = 1..10000 (first 1000 terms from Giovanni Resta)
FORMULA
a(n) = 2*(A105653(n) + 1) = 2*A124409(n). - Hugo Pfoertner, May 03 2021
PROG
(Python)
import sympy
from sympy import isprime
for n in range(0, 100000, 2):
if isprime(n+1) and isprime(2*n+1) and isprime(3*n+1) and isprime(4*n+1):
print(str(n), end=', ')
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Feb 04 2014
STATUS
approved