A247114 Primes sandwiched between 4-almost primes (A014613).

89, 151, 197, 233, 307, 349, 461, 491, 569, 571, 739, 857, 859, 1013, 1061, 1097, 1277, 1291, 1303, 1483, 1667, 1747, 1831, 1913, 1973, 2003, 2131, 2357, 2503, 2531, 2621, 2683, 3011, 3067, 3163, 3209, 3229, 3259, 3271, 3581, 3797, 3929, 4013, 4027, 4073, 4219, 4327, 4597, 4793, 4877, 4903

Offset

1,1

Comments

Primes p such that p - 1 and p + 1 are 4-almost primes.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

89 - 1 = 2^3*11, 89 + 1 = 2*3^2*5.

Mathematica

Select[Prime[Range[1000]], 4 == PrimeOmega[# - 1] == PrimeOmega[# + 1] &]

Prog

(PARI) forprime(p= 1, 5000, if(4==bigomega(p-1)&&4==bigomega(p+1), print1(p", ")))
(PARI) is(n)=bigomega(n-1)==4 && bigomega(n+1)==4 && isprime(n) \\ Charles R Greathouse IV, Apr 27 2015

Crossrefs

Cf. A014612, A014613, A046314, A154598, A063644, A247088.

Sequence in context: A031416 A340307 A353249 * A075589 A142031 A302003

Adjacent sequences: A247111 A247112 A247113 * A247115 A247116 A247117

Keyword

nonn

Author

Zak Seidov, Jan 10 2015

Status

approved