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A026102
a(n) = T(2n-1,n), where T is the array in A026098.
0
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
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. A033286. [R. J. Mathar, Oct 22 2008]
Sequence in context: A359696 A134978 A115742 * A338024 A144519 A066995
KEYWORD
nonn
EXTENSIONS
Corrected and extended by Michel Marcus, Sep 04 2019
STATUS
approved