OFFSET
1,1
COMMENTS
Product of the first n primes which are natural primes which are not Gaussian primes. Product of the first n primes congruent to 1 or 2 modulo 4. Product of the first n primes of form x^2+y^2. Product of the first n primes p such that -1 is a square mod p. Factors of primorials (A002110) not divisible by natural primes which are also Gaussian primes.
Essentially twice A006278.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..300
FORMULA
EXAMPLE
a(10) = 2 * 5 * 13 * 17 * 29 * 37 * 41 * 53 * 61 * 73 = 22945864100770.
MATHEMATICA
Rest@ FoldList[#1*#2 &, 1, Select[ Prime@ Range@ 30, Mod[#, 4] != 3 &]] (* Robert G. Wilson v *)
PROG
(PARI) pp(v)=my(t=1); vector(#v, i, t*=v[i])
pp(select(n->n%4<3, primes(20))) \\ Charles R Greathouse IV, Apr 21 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jonathan Vos Post, Feb 07 2011
EXTENSIONS
Terms corrected by Robert G. Wilson v, Feb 11 2011
STATUS
approved