A038597 Numbers whose square is a difference between 2 positive cubes in at least one way.

13, 28, 49, 104, 147, 181, 189, 224, 351, 361, 388, 392, 507, 549, 588, 676, 756, 832, 1029, 1176, 1323, 1369, 1425, 1448, 1512, 1625, 1792, 1862, 1911, 1922, 2299, 2355, 2521, 2808, 2883, 2888, 3104, 3136, 3185, 3216, 3500, 3721, 3969, 4056, 4103, 4332

Offset: 1

Author

Jeff Burch

Keywords

• nonn

Links

• Donovan Johnson, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A038593-A038598.

Programs

PARI

is(n)=my(N=n^2); for(k=sqrtnint(N,3)+1,(sqrtint(12*N-3)+3)\6, if(ispower(N-k^3,3), return(1))); 0 \\ Charles R Greathouse IV, Oct 28 2013

PARI

mm=820188; cb=vector(mm); for(i=1, mm, cb[i]=i^3); mb=1420608; v=vector(mb); mx=mb^2; for(i=1, mm-1, for(j=i+1, mm, d=cb[j]-cb[i]; if(d<=mx, if(issquare(d, &r), v[r]=1), next(2)))); c=0; for(n=1, mb, if(v[n]==1, c++; write("b038597.txt", c " " n))) \\ Donovan Johnson, Oct 31 2013

Formula

a(n) = sqrt(A038596(n)). - M. F. Hasler, Oct 05 2013

Extensions

More terms from Jud McCranie