A373972 a(n) = 1 if n can be represented as a sum of 2 nonnegative cubes, otherwise 0.

1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1

Offset

0

Comments

Differs from A025446 first at n=1729, where A025446(1729) = 2, while a(1729) = 1.

Links

Antti Karttunen, Table of n, a(n) for n = 0..100080

Index entries for characteristic functions

Formula

a(n) = signum(A025446(n)) = [A025446(n) > 0], where [ ] is the Iverson bracket.

a(n) >= A373971(n).

Prog

(PARI) A373972(n) = if(0==n, 1, my(L=sqrtnint(n-1, 3)+1, U=sqrtnint(4*n, 3)); fordiv(n, m, if(L<=m && m<=U, my(ell=(m^2-n/m)/3); if(denominator(ell)==1 && issquare(m^2-4*ell), return(1)))); 0); \\ After Charles R Greathouse IV's Apr 16 2013 program in A004999.

Crossrefs

Characteristic function of A004999.

Cf. A010057, A025446, A373971.

Sequence in context: A179830 A266216 A025446 * A266300 A266605 A016421

Adjacent sequences: A373965 A373970 A373971 * A373973 A373974 A373975

Keyword

nonn

Author

Antti Karttunen, Jun 24 2024

Status

approved