OFFSET
1,1
COMMENTS
The three primes are of the form 4*k + 1.
LINKS
Ray Chandler, Table of n, a(n) for n = 1..10000 (first 1000 terms from Colin Barker)
EXAMPLE
1105 is in the sequence because x^2 + y^2 = 1105 = 5*13*17 has solutions (x,y) = (4,33), (9,32), (12,31) and (23,24).
PROG
(PARI)
dop(d, nmax) = {
my(L=List(), v=vector(d, m, 1)~, f);
for(n=1, nmax,
f=factorint(n);
if(#f~==d && f[1, 1]>2 && f[, 2]==v && f[, 1]%4==v, listput(L, n))
);
Vec(L)
}
dop(3, 15000)
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Nov 15 2015
STATUS
approved