A026102 a(n) = T(2n-1,n), where T is the array in A026098.

1, 6, 15, 28, 55, 78, 119, 152, 230, 290, 372, 444, 574, 645, 752, 901, 1062, 1159, 1273, 1491, 1606, 1817, 1992, 2314, 2522, 2828, 2987, 3210, 3270, 3616, 4191, 4323, 4658, 5004, 5364, 5738, 6123, 6357, 6847, 7266, 7697, 7964, 8595, 8685, 9259, 9552, 10339, 10927, 11577, 11908

Offset

1,2

Links

Table of n, a(n) for n=1..50.

Formula

a(n) = A026098(A001844(n)). - Sean A. Irvine, Sep 16 2019

Mathematica

T[1, 1] = 1; T[2, 1] = 3; T[2, 2] = 2; T[n_, 1] := Prime[n];
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]]]];
a[n_] := T[2n-1, n]; (* Jean-François Alcover, Sep 05 2019 *)

Prog

(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

Crossrefs

Cf. A001844, A026098.

Cf. A033286. [R. J. Mathar, Oct 22 2008]

Sequence in context: A359696 A134978 A115742 * A338024 A144519 A066995

Adjacent sequences: A026099 A026100 A026101 * A026103 A026104 A026105

Keyword

nonn

Author

Clark Kimberling

Extensions

Corrected and extended by Michel Marcus, Sep 04 2019

Status

approved