%A235155 by Christopher M. Conrey, Jan 25, 2022. %Generate all unique triplets of numbers with digits 0..9 to create %sequences from. combos = nchoosek(0:9,3); combos(sum(mod(combos,2),2)==0,:) = []; %rm comb's where all numbers are even. combos(sum(mod(combos,3),2)==0,:) = []; %rm comb's where all numbers are div3. list = []; for k = 3:7 %iterate over all k-digit perms of #'s in combos. 7 yields almost 20k terms inds_proto = dec2base(1:(3^k)-2,3)-'0'+1; %find all k-digit triple perms in base 3, convert to indices. inds = []; for i = 1:length(inds_proto) bit = inds_proto(i,:); if length(unique(bit,'sorted'))==3 %ensure number has 3 distinct digits. inds = [inds;bit]; end end for triple = combos' vec = str2num(char(triple(inds)+'0')); %generate numbers with 3 distinct dig's vec(vec<10^(k-1)) = []; %Remove numbers with leading 0's. list = [list; vec(isprime(vec))]; %append numbers if prime. end end list = sort(list);