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a(n) is the largest number that is the digit sum of an n-digit cube.
4

%I #31 Jul 04 2024 04:59:11

%S 8,10,18,28,28,44,46,54,63,73,80,82,98,100,109,118,125,136,144,154,

%T 154,163,172,181,190,190,199,208,217,226,235,243,253,260,262,278

%N a(n) is the largest number that is the digit sum of an n-digit cube.

%H Kevin Ryde, <a href="/A373727/a373727.c.txt">C Code</a>

%e a(7) = 46 because 46 is the largest digital sum encountered among all 7-digit cubes (attained at 3 cubes: 3869893, 7880599, 8998912).

%t Table[Max@

%t Map[Total@IntegerDigits[#^3] &,

%t Range[Ceiling@CubeRoot[10^(n - 1)], CubeRoot[10^n - 1]]], {n, 15}]

%o (Python)

%o from sympy import integer_nthroot

%o def A373727(n): return max(sum(int(d) for d in str(m**3)) for m in range(1+integer_nthroot(10**(n-1)-1,3)[0],1+integer_nthroot(10**n-1,3)[0])) # _Chai Wah Wu_, Jun 26 2024

%o (C) /* See links. */

%Y Cf. A018005, A061439.

%Y Other powers: A371728, A373914, A374025, A373994.

%K nonn,base,more

%O 1,1

%A _Zhining Yang_, Jun 15 2024