1,2

The number of divisors of the 4th perfect number is equal to 2*A000043(4)=A061645(4)=14.

a(n)=A133024(n), written in base 2. Also, for n=1 .. 14: If n<=(A000043(4)=7) then a(n) is the concatenation of the digit "1" and n-1 digits "0" else a(n) is the concatenation of A000043(4)=7 digits "1" and (n-1-A000043(4)) digits "0".

The structure of divisors of 8128 (See A133024)

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n ... Divisor . Formula ....... Divisor written in base 2 ...............

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1)......... 1 = 2^0 ........... 1

2)......... 2 = 2^1 ........... 10

3)......... 4 = 2^2 ........... 100

4)......... 8 = 2^3 ........... 1000

5)........ 16 = 2^4 ........... 10000

6)........ 32 = 2^5 ........... 100000

7)........ 64 = 2^6 ........... 1000000 ... (The 4th superperfect number)

8)....... 127 = 2^7 - 2^0 ..... 1111111 ... (The 4th Mersenne prime)

9)....... 254 = 2^8 - 2^1 ..... 11111110

10)...... 508 = 2^9 - 2^2 ..... 111111100

11)..... 1016 = 2^10- 2^3 ..... 1111111000

12)..... 2032 = 2^11- 2^4 ..... 11111110000

13)..... 4064 = 2^12- 2^5 ..... 111111100000

14)..... 8128 = 2^13- 2^6 ..... 1111111000000 ... (The 4th perfect number)

For more information see A133024 (Divisors of 8128). Cf. A000043, A000079, A000396, A000668, A019279, A061645, A061652.

Sequence in context: A136872 A119084 A136875 this_sequence A029800 A100061 A125858

Adjacent sequences: A135651 A135652 A135653 this_sequence A135655 A135656 A135657

base,nonn,fini,full

Omar E. Pol (info(AT)polprimos.com), Feb 23 2008, Mar 03 2008