Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A131866
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A131866 Distance of n-th semiprime to nearest square. +0
1
0, 2, 0, 1, 2, 1, 4, 3, 0, 1, 3, 2, 1, 2, 3, 3, 0, 2, 6, 7, 6, 2, 1, 5, 7, 4, 1, 4, 5, 6, 9, 7, 6, 5, 6, 10, 6, 3, 2, 0, 1, 2, 8, 11, 10, 3, 2, 1, 1, 2, 11, 11, 10, 8, 3, 0, 8, 9, 13, 11, 9, 2, 5, 6, 7, 9, 10, 13, 12, 11, 10, 8, 7, 6, 4, 1, 10, 12, 9, 7, 3, 2, 3, 6, 9, 11, 15, 11, 2, 0, 2, 6, 9, 10, 12 (list; graph; listen)
OFFSET

1,2

COMMENT

This to semiprimes A001358 as A047972 is to primes A000040.

For each semiprime, find the closest square (preceding or succeeding); subtract, take absolute value.

FORMULA

a(n)=A053188(A001358(n)) (corrected by R. J. Mathar, Nov 19 2007).

EXAMPLE

a(1) = 0 because the 1st semiprime is 4, which is a square.

a(2) = 2 because the 2nd semiprime is 6, and |6-4| = 2 where 4 is the nearest square to 6.

a(3) = 0 because the 3rd semiprime is 9, which is a square.

a(4) = 1 because the 4th semiprime is 10, and |10-9| = 1 where 9 is the nearest square to 10.

CROSSREFS

Cf. A001358, A047972, A053188.

Sequence in context: A020513 A029276 A109248 this_sequence A036862 A094238 A127793

Adjacent sequences: A131863 A131864 A131865 this_sequence A131867 A131868 A131869

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post (jvospost2(AT)yahoo.com), Oct 04 2007

EXTENSIONS

More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 24 2007

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified July 26 13:41 EDT 2008. Contains 142293 sequences.


AT&T Labs Research