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A227227
Numbers k such that k*sum_of_digits(k) is a perfect cube.
1
0, 1, 8, 81, 125, 512, 1000, 1331, 2592, 6400, 8000, 10125, 19683, 20736, 34300, 35937, 36125, 46656, 59319, 74088, 81000, 123823, 125000, 157464, 185193, 268912, 279936, 328509, 373248, 421875, 431244, 469567, 474552, 481474, 512000, 592704, 658503, 795906
OFFSET
1,3
EXAMPLE
512*(5+1+2) = 4096 = 16^3. Hence, 512 is a term of the sequence.
MATHEMATICA
Select[Range@ 1000000, IntegerQ@ Power[# Plus @@ IntegerDigits@ #, 1/3] == True &] (* Michael De Vlieger, Mar 23 2015 *)
PROG
(Python)
def DS(n):
return sum(int(i) for i in str(n))
def a(n):
k = 0
nDSn = n * DS(n)
while k <= n:
if k**3 == nDSn:
return True
if k**3 > nDSn:
return False
k += 1
[n for n in range(10**5) if a(n)]
# Simplified by Derek Orr, Mar 22 2015
(Sage)
n=100000 # change n for more terms
[x for x in [0..n] if floor((x*sum(Integer(x).digits(base=10)))^(1/3))==(x*sum(Integer(x).digits(base=10)))^(1/3)] # Tom Edgar, Sep 21 2013
(PARI) for(n=0, 10^6, if((n==0) || ispower(n*sumdigits(n), 3), print1(n, ", "))) \\ Derek Orr, Mar 22 2015
CROSSREFS
Cf. A227224.
Sequence in context: A274855 A301939 A302417 * A303184 A302325 A303018
KEYWORD
nonn,base,easy
AUTHOR
Derek Orr, Sep 19 2013
STATUS
approved