OFFSET
1,1
COMMENTS
a(2)-a(9) from Chuck Gaydos.
LINKS
Chris K. Caldwell and G. L. Honaker, Jr., Prime Curio for 406
EXAMPLE
a(1)=406 because 406 is the smallest number in the first set of three consecutive triangular numbers that are sphenic, i.e., {406=2*7*29, 435=3*5*29, 465=3*5*31}.
MATHEMATICA
t[n_] := n*(n+1)/2; spQ[n_] := FactorInteger[n][[;; , 2]] == {1, 1, 1}; Select[Partition[t /@ Range[170000], 3, 1], AllTrue[#, spQ] &][[;; , 1]] (* Amiram Eldar, Oct 06 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Oct 05 2021
EXTENSIONS
a(10)-a(25) from Alois P. Heinz, Oct 05 2021
STATUS
approved