This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A118724 Chen primes for which the multiplicative digital root is also a Chen prime. 0
 2, 3, 5, 7, 13, 17, 31, 37, 53, 71, 113, 131, 137, 157, 211, 311, 317, 359, 389, 431, 557, 571, 751, 827, 839, 953, 983, 1117, 1151, 1297, 1367, 1511, 1553, 1621, 1637, 1759, 2111, 2179, 2213, 2269, 2339, 2393, 2699, 2719, 2969, 2971, 3167, 3221, 3329, 3511 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 157 is in the sequence because (1) it is a Chen prime and (2) the multiplicative digital root 5 is also a Chen prime. MATHEMATICA mdr[n_] := NestWhile[Times @@ IntegerDigits@# &, n, # > 9 &]; chenQ[n_] := PrimeQ[n] && Plus @@ Last /@ FactorInteger[n + 2] < 3; Select[ Prime@ Range@500, chenQ@ mdr@# && chenQ@# &] (* Robert G. Wilson v *) CROSSREFS Cf. A109611. Sequence in context: A117159 A134873 A172979 * A046732 A293663 A046703 Adjacent sequences:  A118721 A118722 A118723 * A118725 A118726 A118727 KEYWORD base,nonn AUTHOR Luc Stevens (lms022(AT)yahoo.com), May 21 2006 EXTENSIONS More terms from Robert G. Wilson v, May 22 2006 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.

Last modified January 18 18:45 EST 2018. Contains 297864 sequences.