A291446 Squarefree triprimes of the form p*q*r such that p + q + r + 1 is prime.
30, 42, 66, 78, 102, 110, 138, 182, 186, 222, 230, 246, 266, 282, 290, 318, 366, 374, 402, 434, 438, 498, 506, 518, 530, 582, 590, 602, 606, 618, 638, 642, 710, 782, 786, 806, 854, 890, 906, 942, 962, 1002, 1010, 1022, 1034, 1038, 1106, 1118, 1146, 1158, 1166, 1178, 1298
Offset: 1
Keywords
Examples
42 = 2*3*7 and 2 + 3 + 7 + 1 is prime, so 42 is a term. 402 = 2*3*67 and 2 + 3 + 67 + 1 is prime, so 402 is a term.
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Programs
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GAP
A291446:=List(Filtered(Filtered(List(Filtered(List([1..10^6],Factors),i->Length(i)=3),Set),j->Length(j)=3),i->IsPrime(Sum(i)+1)),Product); # Muniru A Asiru, Aug 29 2017
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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+3), listput(v, 2*p*q)))); Set(v) \\ Charles R Greathouse IV, Aug 29 2017
Comments