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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

It appears that this sequence is finite.

LINKS

Table of n, a(n) for n=1..9.

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

Cf. A028839, A061209, A115518, A130680.

Sequence in context: A042410 A110207 A223205 * A161530 A161954 A162369

Adjacent sequences:  A257783 A257784 A257785 * A257787 A257788 A257789

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

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Last modified April 16 12:45 EDT 2021. Contains 343037 sequences. (Running on oeis4.)