login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A010751 Up 1, down 2, up 3, down 4, ... 0
0, 1, 0, -1, 0, 1, 2, 1, 0, -1, -2, -1, 0, 1, 2, 3, 2, 1, 0, -1, -2, -3, -2, -1, 0, 1, 2, 3, 4, 3, 2, 1, 0, -1, -2, -3, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5, -6, -5, -4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

LINKS

Table of n, a(n) for n=0..80.

FORMULA

a(n)=x+1-(sign(x(2x+1)-y(2y+1)))*(n-2x^2-3x-1) where x=floor((-1-sqrt(1+8n))/4), y=-floor((1-sqrt(1+8n))/4), sign(x)=abs(x)/x when x is not 0 and sign(0)=0, floor(x)=the greatest integer less than or equal to x, sqrt(x)=the principal square root of x and abs(x)=the absolute value (or magnitude) of x. - Mark Spindler, Mar 25 2004

MATHEMATICA

n=(the index); x = -1; y = 0; While[n != 0, While[y != x && n != 0, y--; n-- ]; While[y != -x && n != 0, n--; y++ ]; x-- ]; Print[ -y] provided by Gregory Puleo n = (the index); a = Floor[(-1 - Sqrt[1 + 8* n])/4]; b = -Floor[(1 - Sqrt[1 + 8*n])/4]; a + 1 - Sign[a*(2*a + 1) - b*(2*b + 1)]*(n - 2*a^2 - 3*a - 1) (provided by Mark Spindler)

CROSSREFS

Sequence in context: A054848 A194525 A065368 * A194523 A180714 A170959

Adjacent sequences:  A010748 A010749 A010750 * A010752 A010753 A010754

KEYWORD

sign

AUTHOR

David Berends (dave(AT)pgt.com)

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 10 13:27 EST 2016. Contains 279004 sequences.