A235646 Primes p such that b=2*p+1 is semiprime, c=2*b+1 is 3-almost prime and d=2*c+1 is 4-almost prime.
43, 1429, 2239, 3319, 4831, 6379, 8821, 10501, 11383, 12781, 13003, 14771, 15091, 16063, 16759, 18223, 19213, 19681, 20021, 22571, 24103, 24109, 24571, 25939, 27271, 28933, 29833, 30241, 31723, 33679, 33811, 34381, 34781, 35591, 35863, 39373
Offset: 1
Keywords
Examples
p = 43, b = 87 = 2*29 = A001358(30), c = 175 = 5*5*7 = A014612(43), d = 351 = 3*3*3**13 = A014613(50).
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Select[ Prime@ Range@ 4200,PrimeOmega[2#+1]==2 && PrimeOmega[4#+3]==3 && PrimeOmega[8#+7]==4 &] (* Robert G. Wilson v, Feb 22 2014 *)
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PARI
forprime(p=43,40000,if(bigomega(a=2*p+1)==2&& bigomega(b=2*c+1)==3&&bigomega(c=2*d+1)==4,print(p",")))