OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = numerator ((3*p1*p2*p3)/(p2*p3 + p1*p3 + p1*p2)) with p1 = prime(n), p2 = prime(n + 1), p3 = prime(n + 2).
a(n) = p1*p2*p3 if p1 == p2 == p3 (mod 3), otherwise 3*p1*p2*p3. - Robert Israel, Jul 29 2024
EXAMPLE
MAPLE
q:= proc(a, b, c) if nops({a, b, c} mod 3) = 1 then a*b*c else 3*a*b*c fi end proc:
P:= [seq(ithprime(i), i=1..102)]:
seq(q(P[i], P[i+1], P[i+2]), i=1..100); # Robert Israel, Jul 29 2024
PROG
(PARI) hm3(x, y, z)=3/(1/x+1/y+1/z);
p1=2; p2=3; forprime(p3=5, 150, print1(numerator(hm3(p1, p2, p3)), ", "); p1=p2; p2=p3)
CROSSREFS
KEYWORD
AUTHOR
Hugo Pfoertner, Jan 19 2020
STATUS
approved