A348185 Smallest number k in a set of three consecutive triangular numbers that are sphenic.
406, 861, 39621, 2166321, 3924201, 11146281, 14804961, 19198306, 73951041, 83417986, 97951006, 209643526, 310415986, 522339681, 526225461, 583333246, 611153241, 801460666, 1601581906, 2520251506, 2690954841, 4455349606, 6681853401, 9895642221, 13878029901
Offset: 1
Keywords
Examples
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}.
Links
- Chris K. Caldwell and G. L. Honaker, Jr., Prime Curio for 406
Crossrefs
Programs
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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 *)
Extensions
a(10)-a(25) from Alois P. Heinz, Oct 05 2021
Comments