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 A284359 #22 Mar 19 2023 23:37:44
%S A284359 1,2,3,4,4,4,5,6,6,6,6,6,7,8,8,8,8,8,8,8,9,10,10,10,10,10,10,10,10,10,
%T A284359 11,12,12,12,12,12,12,12,12,12,12,12,13,14,14,14,14,14,14,14,14,14,14,
%U A284359 14,14,14,15,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,17
%N A284359 Double triangle (2*n+2 terms by row). Every row is 2*n + 1 followed by 2*n + 1 times 2*n + 2.
%C A284359 In essence the same as A167991. - _R. J. Mathar_, Mar 27 2017
%F A284359 a(n) = A167381(n+1) - A167381(n).
%e A284359 1, 2,
%e A284359 3, 4, 4, 4,
%e A284359 5, 6, 6, 6, 6, 6,
%e A284359 7, 8, 8, 8, 8, 8, 8, 8,
%e A284359 9, 10, 10, 10, 10, 10, 10, 10, 10, 10,
%e A284359 ... .
%e A284359 The row sum is A000466(n+1).
%t A284359 Table[2 n + 2 - Boole[k == 1], {n, 0, 8}, {k, 2 n + 2}] // Flatten (* _Michael De Vlieger_, Mar 25 2017 *)
%o A284359 (PARI) for(n=0, 10, for(k=1, 2*n + 2, print1(2*n + 2 - (k==1), ", ");); print();) \\ _Indranil Ghosh_, Mar 26 2017, translated from Mathematica code
%o A284359 (Python)
%o A284359 for n in range(0, 11):
%o A284359 print([2*n + 2 -(k==1) for k in range(1, 2*n + 3)])
%o A284359 # _Indranil Ghosh_, Mar 26 2017
%Y A284359 Cf. A000466, A005408, A103517 (main diagonal), A167381.
%K A284359 nonn,tabf
%O A284359 0,2
%A A284359 _Paul Curtz_, Mar 25 2017