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A038597
Numbers whose square is a difference between 2 positive cubes in at least one way.
12
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
1,1
LINKS
FORMULA
a(n) = sqrt(A038596(n)). - M. F. Hasler, Oct 05 2013
PROG
(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
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Jud McCranie
STATUS
approved