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A257786
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Numbers n such that the square root of the sum of the digits times the sum of the digits of n in some power equal n.
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0
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OFFSET
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1,3
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COMMENTS
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It appears that this sequence is finite.
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LINKS
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Table of n, a(n) for n=1..9.
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EXAMPLE
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376 = sqrt(3+7+6)*(3^2+7^2+6^2).
13131 = sqrt(1+3+1+3+1)*(1^7+3^7+1^7+3^7+1^7).
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PROG
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(Python)
def moda(n, a):
....kk = 0
....while n > 0:
........kk= kk+(n%10)**a
........n =int(n//10)
....return kk
def sod(n):
....kk = 0
....while n > 0:
........k= kk+(n%10)
........n =int(n//10)
....return kk
for a in range (1, 10):
for c in range (1, 10**8):
if c**2==sod(c)*moda(c, a)**2:
print (a, c, sod(c), moda(c, a))
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CROSSREFS
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Cf. A028839, A061209, A115518, A130680.
Sequence in context: A042410 A110207 A223205 * A161530 A161954 A162369
Adjacent sequences: A257783 A257784 A257785 * A257787 A257788 A257789
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KEYWORD
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base,nonn,more
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AUTHOR
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Pieter Post, May 08 2015
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EXTENSIONS
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a(6) from Giovanni Resta, May 09 2015
a(7)-a(9) from Chai Wah Wu, Nov 29 2015
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STATUS
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approved
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