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 A329331 #23 Feb 16 2025 08:33:58
%S A329331 0,0,0,0,1,0,0,2,2,0,0,3,8,3,0,0,4,10,10,4,0,0,5,16,9,16,5,0,0,6,18,
%T A329331 20,20,18,6,0,0,7,24,23,32,23,24,7,0,0,8,26,30,36,36,30,26,8,0,0,9,64,
%U A329331 29,48,33,48,29,64,9,0,0,10,66,72,52,54,54,52,72,66,10,0,0,11,72,75,128,51,40,51,128,75,72,11,0
%N A329331 Binary operation over the nonnegative integers, distributive over A003987(.,.), such that A(2^i, 2^j) = 2^A054237(i,j). Square array A(n,k), n >= 0, k >= 0, read by descending antidiagonals.
%C A329331 This sequence defines a multiplication operation that goes with bitwise exclusive-or (A003987) as addition operation to form a ring over the nonnegative integers. It is isomorphic to the polynomial ring GF(2)[x,y], as is the ring defined in A329329.
%C A329331 The ring defined by A329329 is unusual in that it has A059897(.,.) as its addition operation, given that A059897 has more similarities to integer multiplication. A003987, which is isomorphic to A059897 as a binary operation, seems a more standard choice for an addition operator.
%C A329331 However, as explained in A329329, A059897 has a natural choice for mapping a generating set to the 2-dimensions (x and y) of the generating set for the additive group of GF(2)[x,y]. Instead, A003987 needs a pairing function to map its most natural generating set {2^k: k >= 0} onto {x^i * y^j: i >= 0, j >= 0}.
%C A329331 The choice made here was to map 2^k onto the 2 dimensions of x^i * y^j, by proceeding through x and y dimensions as when reading an array by antidiagonals. 2^0 = 1 is mapped to (x^0 * y*0) = 1, 2^1 = 2 is mapped to (x^1 * y^0) = x, 2^2 = 4 to (x^0 * y^1) = y, 8 to (x^2 * y^0) = x^2, and so on, 16 mapped to xy, 32 to y^2, 64 to x^3, etc. With this mapping, it can be shown that the result of the multiplying the polynomial images of 2^i and 2^j is the image of 2^A054237(i,j).
%H A329331 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Distributive.html">Distributive</a>
%H A329331 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PairingFunction.html">Pairing Function</a>
%H A329331 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Ring.html">Ring</a>
%H A329331 Wikipedia, <a href="https://en.wikipedia.org/wiki/Generating_set_of_a_group">Generating set of a group</a>
%H A329331 Wikipedia, <a href="https://en.wikipedia.org/wiki/Polynomial_ring">Polynomial ring</a>
%F A329331 A(2^i, 2^j) = 2^A054237(i,j).
%F A329331 A(A003987(n,m), k) = A003987(A(n,k), A(m,k)).
%F A329331 A(n, A003987(m,k)) = A003987(A(n,m), A(n,k)).
%F A329331 Derived formulas:(Start)
%F A329331 A(n,k) = A(k,n).
%F A329331 A(n,0) = A(0,k) = 0.
%F A329331 A(n,1) = A(1,n) = n.
%F A329331 A(n, A(m,k)) = A(A(n,m), k).
%F A329331 (End)
%e A329331 Square array A(n,k) begins:
%e A329331 n\k | 0 1 2 3 4 5 6 7 8 9 10
%e A329331 ----+----------------------------------------------------------------
%e A329331 0 | 0 0 0 0 0 0 0 0 0 0 0
%e A329331 1 | 0 1 2 3 4 5 6 7 8 9 10
%e A329331 2 | 0 2 8 10 16 18 24 26 64 66 72
%e A329331 3 | 0 3 10 9 20 23 30 29 72 75 66
%e A329331 4 | 0 4 16 20 32 36 48 52 128 132 144
%e A329331 5 | 0 5 18 23 36 33 54 51 136 141 154
%e A329331 6 | 0 6 24 30 48 54 40 46 192 198 216
%e A329331 7 | 0 7 26 29 52 51 46 41 200 207 210
%e A329331 8 | 0 8 64 72 128 136 192 200 1024 1032 1088
%e A329331 9 | 0 9 66 75 132 141 198 207 1032 1025 1098
%e A329331 10 | 0 10 72 66 144 154 216 210 1088 1098 1032
%Y A329331 Cf. A003987, A054237, A059897, A329329.
%K A329331 nonn,tabl
%O A329331 0,8
%A A329331 _Peter Munn_, Nov 10 2019