Number of triangular numbers <= 10^n.

Terms

a(0) =2a(1) =5a(2) =14a(3) =45a(4) =141a(5) =447a(6) =1414a(7) =4472a(8) =14142a(9) =44721a(10) =141421a(11) =447214a(12) =1414214a(13) =4472136a(14) =14142136a(15) =44721360a(16) =141421356a(17) =447213595a(18) =1414213562a(19) =4472135955a(20) =14142135624a(21) =44721359550a(22) =141421356237a(23) =447213595500