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 A269747 #23 Mar 08 2023 16:20:05 %S A269747 0,0,1,5,16,39,80,155,281,476,760,1154,1686,2394,3331,4551,6110,8065, %T A269747 10486,13461,17079,21430,26606,32726,39928,48360,58183,69573,82708, %U A269747 97767,114930,134387,156329,180960,208506,239230,273444,311486,353709,400467,452136,509093,571716,640393,715537 %N A269747 Number of regular tetrahedra in an n-node-per-edge tetrahedral grid. %C A269747 Number of ways to choose 4 points forming a regular tetrahedron out of the binomial(n+2,3) points in a regular tetrahedral grid. %C A269747 The tetrahedra defined by the four points may have any orientation. %C A269747 Similar to A216173, which differs from the present sequence in a mysterious way. %F A269747 It would be nice to have a g.f. - _N. J. A. Sloane_, Mar 21 2016 %Y A269747 Cf. A000332 (2-D version), A216173, A270805, A270806. %K A269747 nonn %O A269747 0,4 %A A269747 _Warren D. Smith_, Mar 21 2016; more terms Mar 23 2016 %E A269747 a(21) changed from 24130 to 21430 by _Anthony Guttmann_, Mar 07 2023