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 A303301 #65 Aug 29 2018 17:59:19 %S A303301 0,0,1,0,1,-3,0,1,-2,0,0,1,-1,1,-8,0,1,0,2,-5,-3,0,1,1,3,-2,0,-15,0,1, %T A303301 2,4,1,3,-9,-8,0,1,3,5,4,6,-3,-2,-24,0,1,4,6,7,9,3,4,-14,-15,0,1,5,7, %U A303301 10,12,9,10,-4,-5,-35,0,1,6,8,13,15,15,16,6,5,-20,-24,0,1,7,9,16,18,21,22,16,15,-5,-9,-48 %N A303301 Square array T(n,k) read by antidiagonals upwards in which row n is obtained by taking the general formula for generalized n-gonal numbers: m*((n - 2)*m - n + 4)/2, where m = 0, +1, -1, +2, -2, +3, -3, ... and n >= 5. Here n >= 0. %C A303301 Note that the formula mentioned in the definition gives several kinds of numbers, for example: %C A303301 Row 0 and row 1 give A317300 and A317301 respectively. %C A303301 Row 2 gives A001057 (canonical enumeration of integers). %C A303301 Row 3 gives 0 together with A008795 (Molien series for 3-dimensional representation of dihedral group D_6 of order 6). %C A303301 Row 4 gives A008794 (squares repeated) except the initial zero. %C A303301 Finally, for n >= 5 row n gives the generalized k-gonal numbers (see Crossrefs section). %H A303301 Alois P. Heinz, <a href="/A303301/b303301.txt">Antidiagonals n = 0..200</a> (first 45 antidiagonals from Robert G. Wilson v) %F A303301 T(n,k) = A194801(n-3,k) if n >= 3. %e A303301 Array begins: %e A303301 ------------------------------------------------------------------ %e A303301 n\m Seq. No. 0 1 -1 2 -2 3 -3 4 -4 5 -5 %e A303301 ------------------------------------------------------------------ %e A303301 0 A317300: 0, 1, -3, 0, -8, -3, -15, -8, -24, -15, -35... %e A303301 1 A317301: 0, 1, -2, 1, -5, 0, -9, -2, -14, -5, -20... %e A303301 2 A001057: 0, 1, -1, 2, -2, 3, -3, 4, -4, 5, -5... %e A303301 3 (A008795): 0, 1, 0, 3, 1, 6, 3, 10, 6, 15, 10... %e A303301 4 (A008794): 0, 1, 1, 4, 4, 9, 9, 16, 16, 25, 25... %e A303301 5 A001318: 0, 1, 2, 5, 7, 12, 15, 22, 26, 35, 40... %e A303301 6 A000217: 0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55... %e A303301 7 A085787: 0, 1, 4, 7, 13, 18, 27, 34, 46, 55, 70... %e A303301 8 A001082: 0, 1, 5, 8, 16, 21, 33, 40, 56, 65, 85... %e A303301 9 A118277: 0, 1, 6, 9, 19, 24, 39, 46, 66, 75, 100... %e A303301 10 A074377: 0, 1, 7, 10, 22, 27, 45, 52, 76, 85, 115... %e A303301 11 A195160: 0, 1, 8, 11, 25, 30, 51, 58, 86, 95, 130... %e A303301 12 A195162: 0, 1, 9, 12, 28, 33, 57, 64, 96, 105, 145... %e A303301 13 A195313: 0, 1, 10, 13, 31, 36, 63, 70, 106, 115, 160... %e A303301 14 A195818: 0, 1, 11, 14, 34, 39, 69, 76, 116, 125, 175... %e A303301 15 A277082: 0, 1, 12, 15, 37, 42, 75, 82, 126, 135, 190... %e A303301 ... %t A303301 t[n_, r_] := PolygonalNumber[n, If[OddQ@ r, Floor[(r + 1)/2], -r/2]]; Table[ t[n - r, r], {n, 0, 11}, {r, 0, n}] // Flatten (* also *) %t A303301 (* to view the square array *) Table[ t[n, r], {n, 0, 15}, {r, 0, 10}] // TableForm (* _Robert G. Wilson v_, Aug 08 2018 *) %Y A303301 Columns 0..2 are A000004, A000012, A023445. %Y A303301 Column 3 gives A001477 which coincides with the row numbers. %Y A303301 Main diagonal gives A292551. %Y A303301 Row 0-2 gives A317300, A317301, A001057. %Y A303301 Row 3 gives 0 together with A008795. %Y A303301 Row 4 gives A008794. %Y A303301 For n >= 5, rows n gives the generalized n-gonal numbers: A001318 (n=5), A000217 (n=6), A085787 (n=7), A001082 (n=8), A118277 (n=9), A074377 (n=10), A195160 (n=11), A195162 (n=12), A195313 (n=13), A195818 (n=14), A277082 (n=15), A274978 (n=16), A303305 (n=17), A274979 (n=18), A303813 (n=19), A218864 (n=20), A303298 (n=21), A303299 (n=22), A303303 (n=23), A303814 (n=24), A303304 (n=25), A316724 (n=26), A316725 (n=27), A303812 (n=28), A303815 (n=29), A316729 (n=30). %Y A303301 Cf. A194801, A195152. %Y A303301 Cf. A317302 (a similar table but with polygonal numbers). %K A303301 sign,tabl %O A303301 0,6 %A A303301 _Omar E. Pol_, Jun 08 2018