OFFSET
1,2
COMMENTS
Previous name was: a(n) triangular, coprime to a(i), i < n.
Sierpinski proved that any finite set of pairwise coprime triangular numbers can be extended by adding an additional triangular number which is coprime to all the elements of the set. Therefore this sequence is infinite. - Amiram Eldar, Mar 01 2019
REFERENCES
W. SierpiĆski, 250 Problems in Elementary Number Theory. New York: American Elsevier, 1970, Problem 42.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
t[n_] := n (n + 1)/2; s = {1}; While[Length[s] < 50, k = s[[-1]] + 1; While[Max[GCD[t[k], t /@ s]] > 1, k++]; AppendTo[s, k]]; t /@ s (* Amiram Eldar, Mar 01 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
New name and more terms from Amiram Eldar, Mar 01 2019
STATUS
approved