%I #40 Jul 14 2024 08:42:50
%S 1,1,1,1,19,17,1,2567,3350,128928,3706896,1290179,100170428,39080794,
%T 61998759572,7833495265,45119290746,581075656330,8672770990,
%U 15792702394898740,594681417768520250,25509154378676494,1642780344643617537867,480931910076867717575
%N a(n) = (A214089(n)^2 - 1) divided by four times the product of the first n primes.
%C When floor(A214089(n) / 2) = A118478(n), a(n) = A215021(n).
%H J. Stauduhar, <a href="/A215085/b215085.txt">Table of n, a(n) for n = 1..30</a>
%F a(n) = (A214089(n)^2 - 1) / (4 * A002110(n)).
%e A214089(14) = 1430083494841, n#_14 = 13082761331670030, and (1430083494841^2 - 1) / (4 * 13082761331670030) = 39080794, so a(14) = 39080794.
%p A215085 := proc(n)
%p (A214089(n)^2-1)/4/A002110(n) ;
%p end proc: # _R. J. Mathar_, Aug 21 2012
%o (Python)
%o from itertools import product
%o from sympy import sieve, prime, isprime, primorial
%o from sympy.ntheory.modular import crt
%o def A215085(n):
%o return (
%o 1
%o if n == 1
%o else (
%o int(
%o min(
%o filter(
%o isprime,
%o (
%o crt(tuple(sieve.primerange(prime(n) + 1)), t)[0]
%o for t in product((1, -1), repeat=n)
%o ),
%o )
%o )
%o )
%o ** 2
%o - 1
%o )
%o // 4
%o // primorial(n)
%o ) # _Chai Wah Wu_, May 31 2022
%o for n in range(1, 16):
%o print(A215085(n), end=", ")
%K nonn
%O 1,5
%A _J. Stauduhar_, Aug 02 2012