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A218013 Numbers that divide the product of the nonzero digits (in base 10) of their square. 5
1, 2, 3, 5, 6, 8, 28, 36, 42, 54, 75, 192, 216, 288, 486, 525, 648, 768, 864, 882, 1728, 2160, 3024, 6048, 6075, 7056, 7680, 17280, 18144, 20736, 30240, 40824, 56448, 60480, 61236, 62208, 64512, 84672, 122472, 138915, 150528, 387072, 408240, 497664, 622080 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10919 (first 473 terms from Chai Wah Wu; terms <= 10^100)

EXAMPLE

For n=5, n^2 is 25; the product of the digits of 25 is 2 * 5 = 10, which is divisible by n=5.

PROG

(PARI) isok(n) = digs = digits(n^2); (prod(i=1, #digs, if (digs[i], digs[i], 1)) % n) == 0; \\ Michel Marcus, Aug 12 2013

(Python)

from operator import mul

from functools import reduce

from gmpy2 import t_mod, mpz

A218013 = [n for n in range(1, 10**6) if not t_mod(reduce(mul, (mpz(d) for d in str(n**2) if d != '0')), n)] # Chai Wah Wu, Aug 23 2014

CROSSREFS

Cf. A002473.

Related to A218072. Subsets of this sequence include A218029 and A218030.

Sequence in context: A275323 A128994 A098211 * A287876 A073673 A179217

Adjacent sequences:  A218010 A218011 A218012 * A218014 A218015 A218016

KEYWORD

nonn,base

AUTHOR

Nels Olson, Oct 18 2012

STATUS

approved

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Last modified June 20 09:27 EDT 2019. Contains 324234 sequences. (Running on oeis4.)