This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A242772 #18 Dec 31 2019 08:21:23 %S A242772 5,11489,32969,33329,33599,42839,58109,93809,96329,114599,180179, %T A242772 272999,309539,334889,401309,540539,633569,717089,784349,820409, %U A242772 870239,879689,907139,948089,989249,991619,994559,1020959,1028579,1044749,1185659,1189649,1245449,1253909 %N A242772 The lesser of twin primes p1 such that 2*p1 + p2 is a prime number (A174913) and also the lesser of other twin primes in A174913. %C A242772 It seems that a(n) == 9 mod 10 for n > 1. %C A242772 a(n) == 9 (mod 10) for n > 1 since if p1 == 1, 3 or 7 (mod 10) then 2*p1 + p2, p2, or 2*p1 + p2 + 2 is divisible by 5, respectively. - _Amiram Eldar_, Dec 31 2019 %H A242772 Amiram Eldar, <a href="/A242772/b242772.txt">Table of n, a(n) for n = 1..10000</a> %e A242772 a(1) = A174913(2) = 5 and 2*5 + 7 = 17 = A174913(3). %t A242772 Select[Range[10^6], And @@ PrimeQ[{#, # + 2,(p = 3*# + 2), p + 2, 3*p + 2}] &] (* _Amiram Eldar_, Dec 31 2019 *) %o A242772 (PARI) isok(p) = isprime(p) && isprime(p+2) && isprime(q=3*p+2) && isprime(q+2) && isprime(3*q+2); \\ _Michel Marcus_, May 23 2014 %Y A242772 Cf. A001359, A174913, A174920, A242773. %K A242772 nonn %O A242772 1,1 %A A242772 _Ivan N. Ianakiev_, May 22 2014