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Perfect cubes whose decimal digits appear in nonincreasing order.
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%I #25 May 22 2022 14:21:56

%S 0,1,8,64,1000,8000,64000,1000000,8000000,64000000,1000000000,

%T 8000000000,64000000000,1000000000000,8000000000000,64000000000000,

%U 1000000000000000,8000000000000000,64000000000000000,1000000000000000000,8000000000000000000,64000000000000000000

%N Perfect cubes whose decimal digits appear in nonincreasing order.

%F a(n) = A004647(n-1)^3.

%e 64 is in the sequence because it is a perfect cube (64 = 4^3) whose digits appear in nonincreasing order.

%t Select[Range[0, 4*10^6]^3, Max@ Differences[IntegerDigits[#]] <= 0 &] (* _Amiram Eldar_, Mar 30 2022 *)

%o (PARI) ok(n) = digits(n) == vecsort(digits(n),,4) && ispower(n,3)

%Y Cf. A004647, A028820, A028864, A234848, A273045.

%Y Intersection of A000578 and A009996.

%K nonn,base

%O 1,3

%A _Antonio Roldán_, Mar 30 2022