login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A307134 Terms of A216427 that are the sum of two coprime terms of A216427. 1
7688, 70688, 95048, 120125, 131072, 186003, 219488, 219501, 265837, 286443, 304175, 371293, 412232, 464648, 465125, 596183, 628864, 699867, 729632, 732736, 834632, 860672, 1104500, 1119371, 1162213, 1173512, 1257728, 1290496, 1318707, 1431125, 1438208, 1472207, 1527752, 1597696, 1601613 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is possible for a term of the sequence to be such a sum in more than one way, e.g., 1119371 = 215168 + 904203 = 366368 + 753003.

There are parametric solutions, and in particular the sequence is infinite. For example, 3^3*(-44100*k^2 - 21140*k + 471)^2 + 5^3*(-26460*k^2 + 4788*k + 865)^2 = 2^3*(132300*k^2 + 8820*k + 3527)^2, and these are coprime unless k==3 (mod 13).

LINKS

Robert Israel, Table of n, a(n) for n = 1..468

EXAMPLE

a(3)=95048 is in the sequence because 95048 = 2^3*109^2 = 45125 + 49923 = 5^3*19^2 + 3^3*43^2, and gcd(45125,49923)=1.

MAPLE

N:= 10^6: # to get terms <= N

A23:= {seq(seq(x^2*y^3, x= 2.. floor(sqrt(N/abs(y)^3))), y=2..floor(N^(1/3)))}: n:=nops(A23):

Res:= NULL:

for k from 1 to n do

  z:= A23[k];

  for i from 1 to n do

    x:= A23[i];

    if 2*x > z then break fi;

    if member(z-x, A23) and igcd(z, x)=1 then  Res:= Res, z; break fi

od od:

Res;

CROSSREFS

Cf. A216427.

Sequence in context: A012082 A184026 A035907 * A183974 A234223 A253923

Adjacent sequences:  A307131 A307132 A307133 * A307135 A307136 A307137

KEYWORD

nonn

AUTHOR

Robert Israel, Mar 26 2019

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 January 25 15:57 EST 2022. Contains 350572 sequences. (Running on oeis4.)