Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A308732
Primes p such that the smallest possible number of 1's in binary representation of a multiple of p equals 3.
1
7, 23, 47, 71, 73, 79, 103, 151, 167, 191, 199, 239, 263, 271, 311, 337, 359, 367, 383, 439, 463, 479, 487, 503, 599, 607, 631, 647, 719, 727, 743, 751, 823, 839, 863, 887, 919, 937, 967, 983, 991, 1031, 1039, 1063, 1087, 1151, 1223, 1231, 1279, 1289, 1303
OFFSET
1,1
COMMENTS
The first few corresponding multipliers that give three 1's are (for the numbers listed above) are 1, 3, 11, 119, 1, 13, 5, 7, 791, 87839, 247, 17970575, 3987, 8048111, 7, 49, 23, 2995944847, 5607007, 7, 2319663.
LINKS
Christian Elsholtz, Almost all primes have a multiple of small Hamming weight, Bull. Aust. Math. Soc. 94 (2016), 224-235.
Eugen J. Ionascu, Florian Luca, and Thomas Merino, On the average value of the minimal Hamming multiple, arXiv:2412.10839 [math.NT], 2024. See pp. 4, 17.
Kenneth B. Stolarsky, Integers whose multiples have anomalous digital frequencies, Acta Arithmetica 38 (1980), 117-128.
MAPLE
filter:= proc(n) local S, r, j;
if not isprime(n) then return false fi;
r:= numtheory:-order(2, n);
if r::even then return false fi;
S:= {seq(2 &^ j mod n, j=1..r)};
S intersect map(t -> -t-1 mod n, S) <> {}
end proc:
select(filter, [seq(i, i=3..2000, 2)]); # Robert Israel, Jun 23 2019
CROSSREFS
Cf. A014662, which enumerates the same sequence for two 1's instead of three.
Sequence in context: A000353 A097149 A185007 * A139035 A002146 A336092
KEYWORD
nonn,base
AUTHOR
Jeffrey Shallit, Jun 20 2019
STATUS
approved