A343085 a(n) is the smallest number that is the sum of n positive cubes in four ways.

13896, 1979, 1252, 626, 470, 256, 224, 225, 226, 227, 221, 222, 223, 203, 204, 205, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205

Offset: 3

Author

Sean A. Irvine, Apr 04 2021

Keywords

• nonn

Comments

This is r(n,3,4) in Alter's notation.

Examples

			a(3) = 13896 = 1^3 + 12^3 + 23^3 = 2^3 + 4^3 + 24^3 = 4^3 + 18^3 + 20^3 = 9^3 + 10^3 + 23^3.
a(4) = 1979 = 1^3 + 5^3 + 5^3 + 12^3 = 2^3 + 3^3 + 6^3 + 12^3 = 5^3 + 5^3 + 9^3 + 10^3 = 6^3 + 6^3 + 6^3 + 11^3.
		

Links

• R. Alter, Computations and generalizations on a remark of Ramanujan, pp. 182-196 of "Analytic Number Theory (Philadelphia, 1980)", ed. M. I. Knopp, Lect. Notes Math., Vol. 899, 1981. See Table 11, page 194.
• Index entries for linear recurrences with constant coefficients, signature (2,-1).

Crossrefs

Cf. A342902, A343081, A343084, A343086.

Programs

Mathematica

LinearRecurrence[{2,-1},{13896,1979,1252,626,470,256,224,225,226,227,221,222,223,203,204,205,171,172},60] (* Harvey P. Dale, Aug 06 2022 *)

Formula

a(n) = n + 152 for n >= 19.