This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Select[Range[0,104],LessEqual@@IntegerDigits[#,12]&] (* Ray Chandler, Jan 06 2014 *) Select[Range[0,120],Min[Differences[IntegerDigits[#,12]]]>-1&] (* Harvey P. Dale, Jul 10 2023 *)
is(n)=vecsort(n=digits(n,12))==n for(n=0,2,forvec(d=vector(n,i,[1,11]),print1(fromdigits(d,12)","),1)) \\ M. F. Hasler, May 05 2020
from itertools import count, islice, combinations_with_replacement def A023753_gen(): # generator of terms yield 0 yield from (int(''.join(c),12) for l in count(1) for c in combinations_with_replacement('123456789ab',l)) A023753_list = list(islice(A023753_gen(),30)) # Chai Wah Wu, Apr 08 2025
12 is 1100 in base 2, 110 in base 3 and 30 in base 4; in each representation every digit is smaller than or equal to the one proceeding so 12 is a term. Similarly, 63 is 111111 in base 2, 2100 in base 3 and 333 in base 4 so it is also a term.
dec(n,b)=my(v=digits(n,b)); v==vecsort(v,,4) is(n)=dec(n,2) && dec(n,3) && dec(n,4) \\ Charles R Greathouse IV, May 03 2016
dec(n,b)=my(v=digits(n,b)); v==vecsort(v,,4) list(lim)=my(v=List([0]),t); for(i=1,logint(lim\1+1,4), t=4^i-1; while(t<=lim, if(dec(t,3), listput(v,t)); t*=4); t=2*4^i-2; while(t<=lim, if(dec(t,3), listput(v,t)); t*=4)); Set(v) \\ Charles R Greathouse IV, May 03 2016
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