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.
%I A377930 #21 Nov 13 2024 08:29:07
%S A377930 0,1,1,0,1,0,2,1,1,2,0,2,0,2,0,1,1,2,2,1,1,0,1,0,2,0,1,0,3,1,1,2,2,1,
%T A377930 1,3,0,3,0,2,0,2,0,3,0,1,1,3,2,1,1,2,3,1,1,0,1,0,3,0,1,0,3,0,1,0,2,1,
%U A377930 1,2,3,1,1,3,2,1,1,2,0,2,0,2,0,3,0,3,0,2,0,2,0
%N A377930 Square array A(n, k), n, k > 0, read by antidiagonals; A(n, k) = max(A007814(n), A007814(k)).
%C A377930 Let K_0 = [0], and for any m > 0, K_m is obtained by arranging four copies of K_{m-1} around a "plus" shape made of m's as follows:
%C A377930 +---------+---+---------+
%C A377930 | | m | |
%C A377930 | | | |
%C A377930 | K_{m-1} | . | K_{m-1} |
%C A377930 | | . | |
%C A377930 | | . | |
%C A377930 +---+ +---------+ +---------+
%C A377930 K_0 = | 0 |, for m > 0, K_m = |m ... m ... m|
%C A377930 +---+ +---------+ +---------+
%C A377930 | | . | |
%C A377930 | | . | |
%C A377930 | K_{m-1} | . | K_{m-1} |
%C A377930 | | | |
%C A377930 | | m | |
%C A377930 +---------+---+---------+
%C A377930 The square array A is the limit of K_m as m tends to infinity.
%F A377930 A(n, k) = A(k, n).
%F A377930 A(n, 0) = A(n, n) = A007814(n).
%e A377930 Array A(n, k) begins:
%e A377930 +---+---+---+---+---+---+---+
%e A377930 | 0 | 1 | 0 | 2 | 0 | 1 | 0 |
%e A377930 +---+ +---+ +---+ +---+
%e A377930 | 1 1 1 | 2 | 1 1 1 |
%e A377930 +---+ +---+ +---+ +---+
%e A377930 | 0 | 1 | 0 | 2 | 0 | 1 | 0 |
%e A377930 +---+---+---+ +---+---+---+
%e A377930 | 2 2 2 2 2 2 2 |
%e A377930 +---+---+---+ +---+---+---+
%e A377930 | 0 | 1 | 0 | 2 | 0 | 1 | 0 |
%e A377930 +---+ +---+ +---+ +---+
%e A377930 | 1 1 1 | 2 | 1 1 1 |
%e A377930 +---+ +---+ +---+ +---+
%e A377930 | 0 | 1 | 0 | 2 | 0 | 1 | 0 |
%e A377930 +---+---+---+---+---+---+---+
%t A377930 A[n_,k_]:=Max[IntegerExponent[n,2],IntegerExponent[k,2]]; Table[A[n-k+1,k],{n,13},{k,n}]//Flatten (* _Stefano Spezia_, Nov 13 2024 *)
%o A377930 (PARI) A(n, k) = max(valuation(n, 2), valuation(k, 2))
%Y A377930 Cf. A003984, A007814, A053398.
%K A377930 nonn,easy,tabl
%O A377930 1,7
%A A377930 _Rémy Sigrist_, Nov 11 2024