A291319 Squarefree triprimes of the form p*q*r such that p+q+r-1 is prime.

42, 70, 78, 110, 114, 130, 154, 170, 222, 230, 258, 310, 322, 370, 374, 402, 406, 410, 418, 442, 470, 474, 530, 582, 598, 610, 618, 638, 646, 654, 670, 682, 730, 742, 754, 762, 782, 826, 830, 874, 902, 970, 978, 986, 994, 1010, 1030, 1034, 1070, 1158, 1222

Offset: 1

Author

Vincenzo Librandi, Aug 23 2017

Keywords

• nonn
• easy

Examples

			42 = 2*3*7 and 2+3+7-1 is prime, so 42 is a term.
418 = 2*11*19 and 2+11+19-1 is prime, so 418 is a term.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A007304.

Programs

Mathematica

With[{nnn=80}, Take[Times@@@Select[Subsets[Prime[Range[nnn]], {3}], PrimeQ[Total[#] - 1] &]//Union, nnn]]

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