A331841 - OEIS

%I #32 Sep 08 2022 08:46:25

%S 0,1,3,6,9,10,18,21,27,30,54,57,60,63,89,90,108,114,126,130,178,180,

%T 189,228,300,356,378,390,630,712,780,900,1170,1299,1300,1890,1953,

%U 2340,2370,2730,3510,3900,3906,4740,7020,7110,7410,7800,8100,8190,9261,11700

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

%H Dimiter Skordev, <a href="/A331841/b331841.txt">Table of n, a(n) for n = 1..138</a> (terms less than 10^7).

%H Dimiter Skordev, <a href="/A331841/a331841.py.txt">Python script</a>

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

%t Prepend[Select[Range[12000], Divisible[FromDigits[IntegerDigits[#, 2], 5], #] &], 0] (* _Amiram Eldar_, Jan 29 2020 *)

%o (PARI) isok(n) = (n == 0) || (fromdigits(digits(n, 2), 5) % n) == 0; \\ _Michel Marcus_, Jan 29 2020

%o (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

%Y 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).

%K base,nonn

%O 1,3

%A _Dimiter Skordev_, Jan 29 2020