The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A163556 Composite numbers such that exactly four distinct permutations of decimal digits are prime. 3
 170, 194, 710, 790, 791, 793, 914, 917, 970, 973, 1003, 1012, 1015, 1016, 1024, 1028, 1030, 1042, 1082, 1090, 1102, 1105, 1106, 1120, 1126, 1135, 1138, 1150, 1157, 1159, 1160, 1162, 1175, 1178, 1183, 1195, 1204, 1208, 1210, 1216, 1234, 1240, 1243, 1258 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(1) = 170 because 170 is composite, the four permutations 17, 71, 107, and 701 are all prime, and no other permutation of 170 is prime. MAPLE filter:= proc(n) local d, Permutor, P, c, i;   if isprime(n) then return false fi;   d:= ilog10(n)+1;   Permutor:= Iterator:-Permute(convert(n, base, 10));   c:= 0;   for P in Permutor do     if isprime(add(P[i]*10^(i-1), i=1..d)) then       c:= c+1;       if c >= 5 then return false fi;     fi   od;   evalb(c=4) end proc: select(filter, [\$10..2000]); # Robert Israel, Aug 10 2020 MATHEMATICA Select[Range[1300], CompositeQ[#]&&Count[FromDigits/@Permutations[ IntegerDigits[ #]], _?PrimeQ]==4&] (* Harvey P. Dale, Oct 26 2015 *) CROSSREFS Cf. A163554, A163555, A163557, A163558, A163559, A163560, A163561, A163562. Sequence in context: A043658 A296892 A045002 * A229467 A218071 A113789 Adjacent sequences:  A163553 A163554 A163555 * A163557 A163558 A163559 KEYWORD easy,nonn,base AUTHOR Gil Broussard, Jul 30 2009 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.

Last modified January 26 19:15 EST 2022. Contains 350599 sequences. (Running on oeis4.)