A343971 - OEIS

%I #16 May 10 2024 02:16:48

%S 1979,2737,3663,4384,4445,4474,4949,5105,5131,5257,5320,5473,5499,

%T 5553,5616,5733,5768,5833,5852,5859,6064,6104,6328,6372,6435,6587,

%U 6643,6832,6883,6912,6974,7000,7030,7120,7217,7371,7560,7686,7777,7840,8099,8108,8281,8316,8344,8379,8414,8505,8568,8927,9016,9018

%N Numbers that are the sum of four positive cubes in four or more ways.

%H David Consiglio, Jr., <a href="/A343971/b343971.txt">Table of n, a(n) for n = 1..20000</a>

%e 3663 = 1^3 + 10^3 + 11^3 + 11^3

%e      = 2^3 +  4^3 +  6^3 + 15^3

%e      = 2^3 +  9^3 +  9^3 + 13^3

%e      = 4^3 +  7^3 +  8^3 + 14^3

%e so 3663 is a term.

%o (Python)

%o from itertools import combinations_with_replacement as cwr

%o from collections import defaultdict

%o keep = defaultdict(lambda: 0)

%o power_terms = [x**3 for x in range(1,50)]

%o for pos in cwr(power_terms,4):

%o     tot = sum(pos)

%o     keep[tot] += 1

%o rets = sorted([k for k,v in keep.items() if v >= 4])

%o for x in range(len(rets)):

%o     print(rets[x])

%Y Cf. A025369, A025407, A343968, A343972, A343987, A344034, A344352.

%K nonn

%O 1,1

%A _David Consiglio, Jr._, May 05 2021