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A270537
Numbers that are equal to their number of digits multiplied by the sum the cubes of the digits.
0
1, 2080, 2376, 2580, 3784
OFFSET
1,2
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
KEYWORD
nonn,base,fini,full
AUTHOR
STATUS
approved