

A341271


a(n) is the least k such that there are distinct primes p,q,r,s such that kp, kq, kr, ks are primes and (p+q)/(r+s) = n.


1



16, 18, 16, 36, 34, 34, 48, 46, 46, 66, 64, 76, 108, 64, 64, 108, 104, 76, 144, 106, 110, 144, 106, 106, 156, 112, 112, 186, 142, 142, 198, 154, 154, 234, 154, 154, 276, 184, 184, 246, 196, 230, 318, 184, 184, 288, 202, 196, 318, 232, 232, 318, 244, 244, 354, 274, 232, 354, 244, 244, 426, 274
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OFFSET

1,1


LINKS



EXAMPLE

a(4) = 36 because 4 = (17+31)/(5+7) where 17,31,5,7 are primes and 3617 = 19, 3631 = 5, 365 = 31 and 367 = 29 are primes, and 36 is the least number k for which such primes exist.


MAPLE

f:= proc(n) local P, i, c1, c2;
P:= select(t > isprime(t) and isprime(nt), {seq(i, i=3..n, 2)});
select(type, {seq(seq(convert(c1, `+`)/convert(c2, `+`), c1 = combinat:choose(P minus c2, 2)), c2 = combinat:choose(P, 2))}, integer)
end proc:
N:= 70: # for a(1)..a(N)
V:= Vector(N): count:= 0:
for n from 2 by 2 while count < N do
for v in f(n) do
if v <= N and V[v] = 0 then V[v]:= n; count:= count+1 fi
od od:
convert(V, list);


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



