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!)
A088040 Smallest fourth power k such that k-1 is divisible by an n-th power, k > 1. 1
16, 81, 81, 81, 2401, 50625, 923521, 15752961, 260144641, 4228250625, 68184176641, 1095222947841, 17557851463681, 281200199450625, 4501401006735361, 72040003462430721, 1152780773560811521 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(2)=a(3)=a(4) as every odd fourth power is == 1 mod (2^4).

LINKS

Table of n, a(n) for n=1..17.

FORMULA

Empirical g.f.: x*(81920*x^7 -75776*x^6 -45184*x^5 +43696*x^4 -2840*x^3 -2530*x^2 +415*x -16) / ((x-1)*(2*x-1)*(4*x-1)*(8*x-1)*(16*x-1)). [Colin Barker, Feb 05 2013]

EXAMPLE

a(5) = 2401 = 7^4 and 7^4 -1 = (2^5)*3*5^2.

a(6) = 50625 = 15^4 and 15^4 -1 = (2^6)*7*113.

CROSSREFS

Cf. A088041.

Sequence in context: A187363 A110892 A202880 * A065771 A223951 A041490

Adjacent sequences:  A088037 A088038 A088039 * A088041 A088042 A088043

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Sep 19 2003

EXTENSIONS

Corrected and extended by Ray Chandler, Oct 04 2003

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 04:09 EST 2016. Contains 278993 sequences.