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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 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.)