Number of n-digit triangular numbers.

Terms

a(0) =3a(1) =10a(2) =31a(3) =96a(4) =306a(5) =967a(6) =3058a(7) =9670a(8) =30579a(9) =96700a(10) =305793a(11) =967000a(12) =3057922a(13) =9670000a(14) =30579224a(15) =96699996a(16) =305792239a(17) =966999967a(18) =3057922393a(19) =9669999669a(20) =30579223926a(21) =96699996687a(22) =305792239263a(23) =966999966873