OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
EXAMPLE
3 is a term because 3*5 = x^2 + y^2 + z^2 where x, y, z are integers is not soluble.
6 is a term because 3*5*7*11*13 = x^2 + y^2 + z^2 where x, y, z are integers is not soluble.
4 is not a term because 3*5*7 = x^2 + y^2 + z^2 where x, y, z are integers is soluble, 105 = 1^2 + 2^2 + 10^2.
PROG
(PARI) isA004215(n) = { my(fouri, j) ; fouri=1 ; while( n >=7*fouri, if( n % fouri ==0, j= n/fouri-7 ; if( j % 8==0, return(1) ) ; ); fouri *= 4 ; ) ; return(0) ; }
for(n=2, 1e3, if(isA004215(prod(k=2, n, prime(k))), print1(n, ", ")));
(Python)
from sympy import prime
A269903_list, p = [], 1
for i in range(2, 10**6):
p = (p*prime(i)) % 8
if p == 7:
A269903_list.append(i) # Chai Wah Wu, Mar 07 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Mar 07 2016
STATUS
approved