A345568 - OEIS

%I #8 Jul 31 2021 17:57:50

%S 262,277,292,307,342,357,372,422,437,502,517,532,547,597,612,677,772,

%T 787,852,886,901,916,966,981,1027,1046,1141,1156,1221,1362,1377,1396,

%U 1442,1510,1525,1557,1572,1587,1590,1617,1637,1652,1717,1765,1812,1827,1892

%N Numbers that are the sum of seven fourth powers in two or more ways.

%H Sean A. Irvine, <a href="/A345568/b345568.txt">Table of n, a(n) for n = 1..10000</a>

%e 277 is a term because 277 = 1^4 + 1^4 + 1^4 + 1^4 + 1^4 + 2^4 + 4^4 = 1^4 + 1^4 + 2^4 + 2^4 + 3^4 + 3^4 + 3^4.

%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**4 for x in range(1, 1000)]

%o for pos in cwr(power_terms, 7):

%o     tot = sum(pos)

%o     keep[tot] += 1

%o     rets = sorted([k for k, v in keep.items() if v >= 2])

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

%o         print(rets[x])

%Y Cf. A003341, A345520, A345559, A345569, A345577, A345605, A345824.

%K nonn

%O 1,1

%A _David Consiglio, Jr._, Jun 20 2021