A138697 Primes p such that 42*p-1, 42*p+1 and 48*p-1, 48*p+1 are twin primes.
31, 331, 2971, 4421, 4861, 5309, 5441, 20431, 22381, 23459, 28151, 33911, 37061, 37699, 47491, 66449, 75821, 82799, 83701, 86131, 91961, 106621, 110059, 112289, 130811, 134669, 135461, 141601, 144461, 152959, 153701, 167311, 167759, 171049
Offset: 1
Examples
42*31-1=1301, 42*31+1=1303; 48*31-1=1487, 48*31+1=1489; ...
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..2000
Programs
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Magma
[p: p in PrimesUpTo(1000)| IsPrime(42*p-1) and IsPrime(42*p+1) and IsPrime(48*p-1) and IsPrime(48*p+1)]; // Vincenzo Librandi, Nov 24 2010
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Mathematica
a=42;b=48;Select[Prime[Range[14^4]],PrimeQ[a*#-1]&&PrimeQ[a*#+1]&&PrimeQ[b*#-1]&&PrimeQ[b*#+1]&]
Extensions
More terms from Vincenzo Librandi, Apr 01 2010