login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A247114 Primes sandwiched between 4-almost primes (A014613). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A141938 A267819 A031416 * A075589 A142031 A302003

Adjacent sequences:  A247111 A247112 A247113 * A247115 A247116 A247117

KEYWORD

nonn

AUTHOR

Zak Seidov, Jan 10 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 28 17:37 EDT 2020. Contains 334684 sequences. (Running on oeis4.)