Triangular numbers composed of digits {1,2,5}.

Terms

a(0) =1a(1) =15a(2) =21a(3) =55a(4) =1225a(5) =2211a(6) =5151a(7) =15225a(8) =21115a(9) =22155a(10) =151525a(11) =222111a(12) =255255a(13) =11551221a(14) =12552555a(15) =21115251a(16) =22221111a(17) =51151555a(18) =111221155a(19) =251115255a(20) =2222211111a(21) =2552515525a(22) =111251152551a(23) =122515222515a(24) =222222111111