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 A135654 Divisors of 8128 (the 4th perfect number), written in base 2. 13
 1, 10, 100, 1000, 10000, 100000, 1000000, 1111111, 11111110, 111111100, 1111111000, 11111110000, 111111100000, 1111111000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The number of divisors of the 4th perfect number is equal to 2*A000043(4)=A061645(4)=14. LINKS FORMULA 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". EXAMPLE The structure of divisors of 8128 (see A133024) ------------------------------------------------------------------------- n ... Divisor . Formula ....... Divisor written in base 2 ............... ------------------------------------------------------------------------- 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) MATHEMATICA FromDigits[IntegerDigits[#, 2]]&/@Divisors[8128] (* Harvey P. Dale, Jan 08 2014 *) CROSSREFS For more information see A133024 (Divisors of 8128). Cf. A000043, A000079, A000396, A000668, A019279, A061645, A061652. Sequence in context: A136872 A119084 A136875 * A219112 A232661 A029800 Adjacent sequences:  A135651 A135652 A135653 * A135655 A135656 A135657 KEYWORD base,nonn,fini,full,easy,less AUTHOR Omar E. Pol, Feb 23 2008, Mar 03 2008 STATUS approved

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Last modified May 19 18:35 EDT 2022. Contains 353847 sequences. (Running on oeis4.)