A078586 a(n) is the product of the first n primes of the form 4k+3.

3, 21, 231, 4389, 100947, 3129357, 134562351, 6324430497, 373141399323, 25000473754641, 1775033636579511, 140227657289781369, 11638895555051853627, 1198806242170340923581, 128272267912226478823167, 16290578024852762810542209, 2134065721255711928181029379

Offset: 1

Author

T. D. Noe, Dec 01 2002

Keywords

• easy
• nonn

Comments

a(n)+2 is a prime for n=1,2,3,4,8,10,12,17,19,22,23,53.

Product of first n primes that are also Gaussian primes; product of first n primes that are not of the form x^2+y^2.

Links

• T. D. Noe, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A002110, A006278, A038347.

Partial products of A002145.

Programs

Mathematica

maxN=15; pLst={}; k=0; While[Length[pLst]
				

PARI

a(n)=my(t=1); forprime(p=2,,if(p%4==3, t*=p; if(n--<1,return(t)))) \\ Charles R Greathouse IV, Mar 09 2014