|
Search: id:A006338
|
|
|
| A006338 |
|
An "eta-sequence": [ (n+1)*sqrt(2) + (1/2) ] - [ n*sqrt(2) + (1/2) ].
(Formerly M0087)
|
|
+0
3
|
|
| 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Equals its own "second derivative" (cf. A006337).
Presumably this is the same as the following sequence from Hofstadter's book: the number of triangular numbers between each successive pair of squares. More precisely, a(n) is the number of triangular numbers T such that n^2 <= T < (n+1)^2. E.g. a(3) = 2 because 3^2 <= T < 4^2 permits T(4) = 10 and T(5) = 15 and no other triangular number. - Hugo van der Sanden (hv(AT)crypt.org), May 03 2005.
|
|
REFERENCES
|
Douglas Hofstadter, "Fluid Concepts and Creative Analogies", Chapter 1: "To seek whence cometh a sequence".
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
CROSSREFS
|
Cf. A006337.
Sequence in context: A022300 A105690 A006337 this_sequence A020903 A133083 A083921
Adjacent sequences: A006335 A006336 A006337 this_sequence A006339 A006340 A006341
|
|
KEYWORD
|
nonn,easy,nice
|
|
AUTHOR
|
D. R. Hofstadter
|
|
EXTENSIONS
|
More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 28 2003
|
|
|
Search completed in 0.002 seconds
|
