A331841 When expressed in base 2 and then interpreted in base 5, is a multiple of the original number.

0, 1, 3, 6, 9, 10, 18, 21, 27, 30, 54, 57, 60, 63, 89, 90, 108, 114, 126, 130, 178, 180, 189, 228, 300, 356, 378, 390, 630, 712, 780, 900, 1170, 1299, 1300, 1890, 1953, 2340, 2370, 2730, 3510, 3900, 3906, 4740, 7020, 7110, 7410, 7800, 8100, 8190, 9261, 11700

Offset: 1

Author

Dimiter Skordev, Jan 29 2020

Keywords

• base
• nonn

Examples

			30 = 11110_2; 11110_5 = 780 = 26*30.
		

Links

• Dimiter Skordev, Table of n, a(n) for n = 1..138 (terms less than 10^7).
• Dimiter Skordev, Python script

Crossrefs

Cf. (with base 2 and b): A062845 (b=3), A062846 (b=4), A062847 (b=6), A062848 (b=7), A062849 (b=8), A062850 (b=9), A032533 (b=10).

Programs

Magma

[0] cat [k:k in [1..12000]|Seqint(Intseq(Seqint(Intseq(k, 2))), 5) mod k eq 0]; // Marius A. Burtea, Jan 29 2020

Mathematica

Prepend[Select[Range[12000], Divisible[FromDigits[IntegerDigits[#, 2], 5], #] &], 0] (* Amiram Eldar, Jan 29 2020 *)

PARI

isok(n) = (n == 0) || (fromdigits(digits(n, 2), 5) % n) == 0; \\ Michel Marcus, Jan 29 2020