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 A088687 Numbers that can be represented as j^4 + k^4, with 0 < j < k, in exactly one way. 11
 17, 82, 97, 257, 272, 337, 626, 641, 706, 881, 1297, 1312, 1377, 1552, 1921, 2402, 2417, 2482, 2657, 3026, 3697, 4097, 4112, 4177, 4352, 4721, 5392, 6497, 6562, 6577, 6642, 6817, 7186, 7857, 8962, 10001, 10016, 10081, 10256, 10625, 10657, 11296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..4500 EXAMPLE 17 = 1^4 + 4^4. 635318657 = 133^4 + 134^4 is absent because it is also 59^4 + 158^4 (see A046881, A230562) MAPLE N:= 2*10^4: # for terms <= N V:= Vector(N): for j from 1 while 2*j^4 < N do   for k from j+1 do     r:= j^4 + k^4;     if r > N then break fi;     V[r]:= V[r]+1; od od: select(t -> V[t] = 1, [\$1..N]); \$ Robert Israel, Dec 15 2019 MATHEMATICA lst={}; Do[Do[x=a^4; Do[y=b^4; If[x+y==n, AppendTo[lst, n]], {b, Floor[(n-x)^(1/4)], a+1, -1}], {a, Floor[n^(1/4)], 1, -1}], {n, 4*7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Jan 22 2009 *) PROG (PARI) powers2(m1, m2, p1) = { for(k=m1, m2, a=powers(k, p1); if(a==1, print1(k", ")) ); } powers(n, p) = { z1=0; z2=0; c=0; cr = floor(n^(1/p)+1); for(x=1, cr, for(y=x+1, cr, z1=x^p+y^p; if(z1 == n, c++); ); ); return(c) } CROSSREFS Cf. A003336, A088728. Sequence in context: A197397 A053826 A184982 * A321560 A034678 A065960 Adjacent sequences:  A088684 A088685 A088686 * A088688 A088689 A088690 KEYWORD nonn AUTHOR Cino Hilliard, Nov 22 2003 EXTENSIONS Edited by Don Reble, May 03 2006 STATUS approved

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Last modified November 25 05:28 EST 2020. Contains 338617 sequences. (Running on oeis4.)