A026102 - OEIS

%I #22 Sep 17 2019 03:50:01

%S 1,6,15,28,55,78,119,152,230,290,372,444,574,645,752,901,1062,1159,

%T 1273,1491,1606,1817,1992,2314,2522,2828,2987,3210,3270,3616,4191,

%U 4323,4658,5004,5364,5738,6123,6357,6847,7266,7697,7964,8595,8685,9259,9552,10339,10927,11577,11908

%N a(n) = T(2n-1,n), where T is the array in A026098.

%F a(n) = A026098(A001844(n)). - _Sean A. Irvine_, Sep 16 2019

%t T[1, 1] = 1; T[2, 1] = 3; T[2, 2] = 2; T[n_, 1] := Prime[n];

%t T[n_, k_] := T[n, k] = Module[{m, mp, jtt}, For[m = 1, True, m++, mp = m Prime[n+1-k]; jtt = Join[Table[T[i, j], {i, 1, n-1}, {j, 1, i}] // Flatten, Table[T[n, j], {j, 1, k-1}]]; If[FreeQ[jtt, mp], Return[mp]]]];

%t a[n_] := T[2n-1, n]; (* _Jean-François Alcover_, Sep 05 2019 *)

%o (PARI) lista(nn) = {my(all = []); for (n=1, nn, my(row = getrow(n, all)); if (n % 2, print1(row[(n+1)/2], ", ")); all = Set(concat(all, row)););} \\ uses getrow from A026098; _Michel Marcus_, Sep 04 2019

%Y Cf. A001844, A026098.

%Y Cf. A033286. [_R. J. Mathar_, Oct 22 2008]

%K nonn

%O 1,2

%A _Clark Kimberling_

%E Corrected and extended by _Michel Marcus_, Sep 04 2019