 All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars  perplexus dot info  Simple Sequence (Posted on 2007-05-07) The sequence:

1, 3, 7, 13, 21, ...

What is the 600th member of the series?

What member, above the first, with fewer than 5 digits, is a perfect cube?

What member is a 5-digit palindrome that can also be read as a binary number?

What's the smaller of the two consecutive members that are 1000 apart?

 See The Solution Submitted by Charlie Rating: 4.0000 (2 votes) Comments: ( Back to comment list | You must be logged in to post comments.) No Subject | Comment 3 of 7 | f(x) = sigma(x+2) - 1 where x >= 0 and thus f(0) is the first number of the series.

f(599) = 359401
f(18) = 343 = 73
f(100) = 10101 <-- a palindromic "binary" number
[f(4) = 21, in binary is also 10101;
f(5) = 31, in binary is the five-digit palindrome 11111]
(499) = 249501; f(500) = 250501; f(500) - f(499) = 1000

Edited on May 7, 2007, 11:13 pm
 Posted by Dej Mar on 2007-05-07 20:51:19 Please log in:

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