A218013 Numbers that divide the product of the nonzero digits (in base 10) of their square.

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

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: A128994 A098211 A349792 * A287876 A073673 A179217

Adjacent sequences: A218010 A218011 A218012 * A218014 A218015 A218016

Keyword

nonn,base

Author

Nels Olson, Oct 18 2012

Status

approved