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

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

p = 43, b = 87 = 2*29 = A001358(30), c = 175 = 5*5*7 = A014612(43), d = 351 = 3*3*3**13 =  A014613(50).

Mathematica

Select[ Prime@ Range@ 4200, PrimeOmega[2#+1]==2 && PrimeOmega[4#+3]==3 && PrimeOmega[8#+7]==4 &] (* Robert G. Wilson v, Feb 22 2014 *)

Prog

(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", ")))

Crossrefs

Subsequence of A238202.

Cf. A000040, A001358, A014612, A014613, A234095.

Sequence in context: A229432 A122575 A014938 * A022220 A297028 A198206

Adjacent sequences: A235643 A235644 A235645 * A235647 A235648 A235649

Keyword

nonn

Author

Zak Seidov, Feb 20 2014

Status

approved