A373971 - OEIS

A373971

a(n) = 1 if n can be represented as a sum of 2 distinct positive cubes, otherwise 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, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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, 0, 1

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OFFSET

COMMENTS

Differs from A025468 first at n=1729, where a(1729) = 1, while A025468(1729) = 2.

LINKS

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

Index entries for characteristic functions

FORMULA

a(n) = signum(A025468(n)) = [A025468(n) > 0], where [ ] is the Iverson bracket.

a(n) <= A373972(n).

a(n) <= A373973(n).

EXAMPLE

a(9) = 1 as 9 = 2^3 + 1^3.

a(35) = 1 as 35 = 3^3 + 2^3.

PROG

(PARI) A373971(n) = if(0==n, n, for(i=ceil(sqrtn(n\2+1, 3)), sqrtn(n-(1/2), 3), if(ispower(n-(i^3), 3), return(1))); 0); \\ After M. F. Hasler's Apr 12 2008 program in A024670.

CROSSREFS

Characteristic function of A024670.

Cf. A010057, A025468, A373972, A373973, A373974 (inverse Möbius transform).

Sequence in context: A297039 A239705 A025468 * A025465 A323514 A369660

Adjacent sequences: A373968 A373969 A373970 * A373972 A373973 A373974

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jun 24 2024

STATUS

approved