login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A274027 Numbers n such that n^4 is the average of a positive cube and a positive fifth power. 0
1, 162, 324, 3888, 11664, 18750, 31250, 32768, 38416, 40000, 160000, 167042, 168750, 253125, 373248, 607500, 911250, 1037232 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that 2*n^4 is of the form x^3 + y^5 where x and y are positive integers.

Sequence is infinite because if m is a term, that is m^4 = (w^3 + z^5)/2 with w and z positive integers, then m*t^15 is also a term for every integer t>1. In fact: (m*t^15)^4 = ((w*t^20)^3 + (z*t^12)^5)/2.

LINKS

Table of n, a(n) for n=1..18.

EXAMPLE

162 = 3*54 is a term because (3*54)^4 = ((18*54)^3 + 54^5)/2.

38416 = 14^4 is a term because (14^4)^4 = ((3*14^5)^3 + (14^3)^5)/2.

PROG

(PARI) isA100293(n) = for(y=1, sqrtnint(n-1, 5), if(ispower(n-y^5, 3), return(1))); 0;

lista(nn) = for(n=1, nn, if(isA100293(2*n^4), print1(n, ", ")));

CROSSREFS

Cf. A000583, A100293.

Sequence in context: A107120 A045010 A085446 * A206210 A044985 A302283

Adjacent sequences:  A274024 A274025 A274026 * A274028 A274029 A274030

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Jun 07 2016

EXTENSIONS

a(11)-a(18) from Giovanni Resta, Jun 07 2016

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
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 23 21:56 EDT 2021. Contains 345402 sequences. (Running on oeis4.)