|
%I #10 Aug 23 2017 03:11:22
%S 42,70,78,110,114,130,154,170,222,230,258,310,322,370,374,402,406,410,
%T 418,442,470,474,530,582,598,610,618,638,646,654,670,682,730,742,754,
%U 762,782,826,830,874,902,970,978,986,994,1010,1030,1034,1070,1158,1222
%N Squarefree triprimes of the form p*q*r such that p+q+r-1 is prime.
%H Charles R Greathouse IV, <a href="/A291319/b291319.txt">Table of n, a(n) for n = 1..10000</a>
%e 42 = 2*3*7 and 2+3+7-1 is prime, so 42 is a term.
%e 418 = 2*11*19 and 2+11+19-1 is prime, so 418 is a term.
%t With[{nnn=80}, Take[Times@@@Select[Subsets[Prime[Range[nnn]], {3}], PrimeQ[Total[#] - 1] &]//Union, nnn]]
%o (PARI) list(lim)=my(v=List()); forprime(p=5,lim\6, forprime(q=3,min(lim\2\p, p-2), if(isprime(p+q+1), listput(v,2*p*q)))); Set(v) \\ _Charles R Greathouse IV_, Aug 23 2017
%Y Subsequence of A007304.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Aug 23 2017
|
