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A257786
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.
0
0, 1, 27, 376, 13131, 234595324075, 54377519037479592374299, 8326623359858152426050700, 1513868951125582592290131113769528
OFFSET
1,3
COMMENTS
It appears that this sequence is finite.
EXAMPLE
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).
PROG
(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))
CROSSREFS
KEYWORD
base,nonn,more
AUTHOR
Pieter Post, May 08 2015
EXTENSIONS
a(6) from Giovanni Resta, May 09 2015
a(7)-a(9) from Chai Wah Wu, Nov 29 2015
STATUS
approved