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”).
%I #21 Sep 09 2017 19:33:47
%S 0,1,1,1,0,1,2,2,2,2,1,1,0,1,1,2,2,1,1,2,2,1,1,1,0,1,1,1,2,2,2,2,2,2,
%T 2,2,2,1,2,1,0,1,2,1,2,3,3,3,3,1,1,3,3,3,3,2,2,1,2,2,0,2,2,1,2,2,3,3,
%U 2,2,3,3,3,3,2,2,3,3,1,2,2,1,2,2,0,2,2,1,2,2,1,2,2,3,3,3,3,1,1,3,3,3,3,2,2,2,1,2,2,1,2,1,0,1,2,1,2,2,1,2
%N Square array T(i,j) giving the number of differing digits in the factorial base representations of i and j, for i >= 0, j >= 0, read by antidiagonals.
%C This table relates to the factorial base representation (A007623) in a somewhat similar way as A101080 relates to the binary system. See A231713 for another analog.
%H Antti Karttunen, <a href="/A230415/b230415.txt">The first 121 antidiagonals of the table, flattened</a>
%F T(n,0) = T(0,n) = A060130(n).
%F Each entry T(i,j) <= A231713(i,j).
%e The top left corner of this square array begins as:
%e 0, 1, 1, 2, 1, 2, 1, 2, 2, 3, 2, ...
%e 1, 0, 2, 1, 2, 1, 2, 1, 3, 2, 3, ...
%e 1, 2, 0, 1, 1, 2, 2, 3, 1, 2, 2, ...
%e 2, 1, 1, 0, 2, 1, 3, 2, 2, 1, 3, ...
%e 1, 2, 1, 2, 0, 1, 2, 3, 2, 3, 1, ...
%e 2, 1, 2, 1, 1, 0, 3, 2, 3, 2, 2, ...
%e 1, 2, 2, 3, 2, 3, 0, 1, 1, 2, 1, ...
%e 2, 1, 3, 2, 3, 2, 1, 0, 2, 1, 2, ...
%e 2, 3, 1, 2, 2, 3, 1, 2, 0, 1, 1, ...
%e 3, 2, 2, 1, 3, 2, 2, 1, 1, 0, 2, ...
%e 2, 3, 2, 3, 1, 2, 1, 2, 1, 2, 0, ...
%e ...
%e For example, T(1,2) = T(2,1) = 2 as 1 has factorial base representation '...0001' and 2 has factorial base representation '...0010', and they differ by their two least significant digits.
%e On the other hand, T(3,5) = T(5,3) = 1, as 3 has factorial base representation '...0011' and 5 has factorial base representation '...0021', and they differ only by their second rightmost digit.
%e Note that as A007623(6)='100' and A007623(10)='120', we have T(6,10) = T(10,6) = 1 (instead of 2 as in A231713, cf. also its Example section), as here we count only the number of differing digit positions, but ignore the magnitudes of their differences.
%t nn = 14; m = 1; While[m! < nn, m++]; m; Table[Function[w, Count[Subtract @@ Map[PadLeft[#, Max@ Map[Length, w]] &, w], k_ /; k != 0]]@ Map[IntegerDigits[#, MixedRadix[Reverse@ Range[2, m]]] &, {i - j, j}], {i, 0, nn}, {j, 0, i}] // Flatten (* _Michael De Vlieger_, Jun 27 2016, Version 10.2 *)
%o (Scheme)
%o (define (A230415 n) (A230415bi (A025581 n) (A002262 n)))
%o (define (A230415bi x y) (let loop ((x x) (y y) (i 2) (d 0)) (cond ((and (zero? x) (zero? y)) d) (else (loop (floor->exact (/ x i)) (floor->exact (/ y i)) (+ i 1) (+ d (if (= (modulo x i) (modulo y i)) 0 1)))))))
%Y The topmost row and the leftmost column: A060130.
%Y Only the lower triangular region: A230417. Related arrays: A230419, A231713. Cf. also A101080, A084558, A230410.
%K nonn,base,tabl
%O 0,7
%A _Antti Karttunen_, Nov 10 2013