Numbers n occurring in binary representation of n*(n+1)/2.

Terms

a(0) =1a(1) =3a(2) =7a(3) =13a(4) =15a(5) =20a(6) =31a(7) =63a(8) =72a(9) =82a(10) =109a(11) =127a(12) =141a(13) =177a(14) =243a(15) =255a(16) =272a(17) =511a(18) =693a(19) =886a(20) =1023a(21) =1056a(22) =1311a(23) =1350a(24) =1480a(25) =2047a(26) =2130a(27) =2378a(28) =3812a(29) =4039