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
Keywords
Examples
89 - 1 = 2^3*11, 89 + 1 = 2*3^2*5.
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Prime[Range[1000]], 4 == PrimeOmega[# - 1] == PrimeOmega[# + 1] &]
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PARI
forprime(p= 1,5000, if(4==bigomega(p-1)&&4==bigomega(p+1), print1(p", ")))
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PARI
is(n)=bigomega(n-1)==4 && bigomega(n+1)==4 && isprime(n) \\ Charles R Greathouse IV, Apr 27 2015
Comments