OFFSET
1,1
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Triangular Number
Eric Weisstein's World of Mathematics, Relatively Prime
FORMULA
a(n) > n+1 for n>1; a(n) > n+2 for n with n mod 3 = 0;
a(n) = n + A130335(n).
PROG
(Python)
from math import gcd
def A130334(n):
k, Tn, Tm = n+1, n*(n+1)//2, (n+1)*(n+2)//2
while gcd(Tn, Tm) != 1:
k += 1
Tm += k
return k # Chai Wah Wu, Sep 16 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, May 28 2007
STATUS
approved