login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A127305 Primes p such that p + (sum of the prime factors of p-1 and p+1) is prime. 1
13, 47, 71, 101, 151, 193, 239, 241, 293, 331, 337, 359, 383, 397, 401, 421, 463, 487, 557, 577, 709, 773, 797, 821, 929, 1019, 1031, 1069, 1093, 1103, 1181, 1217, 1249, 1327, 1367, 1423, 1499, 1571, 1759, 1787, 1789, 1831, 1871, 1877, 1913, 1933, 2053 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

151 is prime, 150 = 2*3*5*5, 152 = 2*2*2*19. 151 + 2+3+5+5 + 2+2+2+19 = 191 is prime, hence 151 is a term.

MATHEMATICA

pspfQ[n_]:=PrimeQ[n+Total[Flatten[Table[#[[1]], {#[[2]]}]&/@Flatten[ FactorInteger[ n+{1, -1}], 1]]]]; Select[Prime[Range[400]], pspfQ] (* Harvey P. Dale, Jan 08 2015 *)

PROG

(MAGMA) [ p: p in PrimesInInterval(3, 2100) | IsPrime(&+[ &+[ k[1]*k[2]: k in Factorization(n)]: n in [p-1..p+1] ] ) ]; /* Klaus Brockhaus, Apr 06 2007 */

CROSSREFS

Sequence in context: A116476 A299716 A035340 * A207992 A274447 A001662

Adjacent sequences:  A127302 A127303 A127304 * A127306 A127307 A127308

KEYWORD

nonn

AUTHOR

J. M. Bergot, Mar 28 2007

EXTENSIONS

Edited and extended by Klaus Brockhaus, Apr 06 2007

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 17 21:47 EDT 2018. Contains 316297 sequences. (Running on oeis4.)