A037096 - OEIS (original) (raw)

When powers of 3 are written in binary (see A004656), under each other as:

000000000001 (1)

000000000011 (3)

000000001001 (9)

000000011011 (27)

000001010001 (81)

000011110011 (243)

001011011001 (729)

100010001011 (2187)

it can be seen that the bits in the n-th column from the right can be arranged in periods of 2^n: 1, 2, 4, 8, ... This sequence is formed from those bits: 1, is binary for 1, thus a(0) = 1. 01, reversed is 10, which is binary for 2, thus a(1) = 2, 0000 is binary for 0, thus a(2)=0, 000110011, reversed is 11001100 = A007088(204), thus a(3) = 204.