A124650 Number of n-digit numbers m such that m and m^10 are zeroless.

3, 14, 42, 141, 399, 1274, 4123, 12688, 39604, 124987, 392908, 1233059, 3869012

Offset

1,1

Links

Table of n, a(n) for n=1..13.

Example

a(3) = 42 because #{113, 118, 125, 142, 144, 166, 172, 176, 186, 187, 195, 228, 244, 263, 268, 296, 315, 334, 357, 367, 376, 383, 387, 388, 396, 426, 467, 527, 563, 573, 574, 662, 764, 773, 783, 788, 863, 883, 885, 892, 976, 992} = 42
Corresponding zeroless 10th powers are:
{339456738992222314849,523383555379856794624,931322574615478515625,
... 318895612267497741289677389824,784328825964927423585898725376,
922819411957263335393616461824}.

Prog

(Python)
from itertools import product
def A124650(n):
    return sum(1 for s in product('123456789', repeat=n) if '0' not in str(int(''.join(s))**10)) # Chai Wah Wu, Mar 24 2020

Crossrefs

Cf. A104264.

Sequence in context: A055650 A367985 A000550 * A291138 A063903 A305009

Adjacent sequences: A124647 A124648 A124649 * A124651 A124652 A124653

Keyword

base,more,nonn

Author

Zak Seidov, Dec 22 2006

Extensions

a(7)-a(8) from Donovan Johnson, Feb 17 2010

a(9)-a(10) from Chai Wah Wu, Mar 24 2020

a(11)-a(13) from Giovanni Resta, Mar 27 2020

Status

approved