A379849 Taxicab numbers that are deficient.

1729, 20683, 40033, 46683, 134379, 149389, 195841, 216027, 216125, 327763, 402597, 439101, 443889, 515375, 558441, 593047, 684019, 704977, 842751, 920673, 984067, 1073375, 1080891, 1195112, 1260441, 1533357, 1566728, 1845649, 2048391, 2301299, 2418271, 2585375, 2622104, 2691451, 3242197

Offset

1,1

Comments

1566728 is the smaller even term in this sequence.

Links

Table of n, a(n) for n=1..35.

Example

1729 = 7*13*19 is a term because it is a Taxicab number (1^3+12^3 = 9^3+10^3) and it is larger than the sum of its proper divisors (1+7+13+19+91+133+247 = 511).
13832 = 2^3*7*13*19 it is not a term because it is a Taxicab number (13832 = 2^3+24^3 = 18^3+20^3) but it is smaller than the sum of its proper divisors 19768.

Mathematica

Select[Import["https://oeis.org/A001235/b001235.txt", "Table"][[;; , 2]], # < 4*10^6 && DivisorSigma[-1, #] < 2 &] (* Amiram Eldar, Jan 04 2025 *)

Crossrefs

Intersection of A001235 and A005100.

Cf. A379466.

Sequence in context: A194263 A379656 A339818 * A293649 A272885 A272935

Adjacent sequences: A379846 A379847 A379848 * A379850 A379851 A379852

Keyword

nonn

Author

Massimo Kofler, Jan 04 2025

Status

approved