A270537 Numbers that are equal to their number of digits multiplied by the sum the cubes of the digits.

1, 2080, 2376, 2580, 3784

Offset

1,2

Links

Table of n, a(n) for n=1..5.

Example

2080 is a term because 2080 = 4 * (2^3 + 0^3 + 8^3 + 0^3);
2376 is a term because 2376 = 4 * (2^3 + 3^3 + 7^3 + 6^3).

Mathematica

Position[ Table[ IntegerLength[ k] Sum[( Floor[k/10^n] - 10 Floor[k/10^(n + 1)])^3, {n, 0, IntegerLength@ k}] - k, {k, 1, 10^6}], 0]
Select[Range[10^5], With[{id=IntegerDigits[#]}, #==Length[id]*Plus@@(id^3)]&] (* Ray Chandler, Apr 01 2016 *)
Select[Range[4000], #==IntegerLength[#]Total[IntegerDigits[#]^3]&] (* Harvey P. Dale, Feb 20 2023 *)

Prog

(PARI) isok(n) = my(d=digits(n)); n == #d*sum(k=1, #d, d[k]^3); \\ Michel Marcus, Mar 25 2016

Crossrefs

Sequence in context: A076425 A249654 A180921 * A076581 A183675 A178272

Adjacent sequences: A270534 A270535 A270536 * A270538 A270539 A270540

Keyword

nonn,base,fini,full

Author

José de Jesús Camacho Medina, Mar 18 2016

Status

approved