A396307 Final terms of length-4 blocks in A280864.

9, 45, 27, 48, 99, 135, 81, 325, 207, 175, 225, 147, 139, 459, 513, 637, 529, 475, 575, 507, 747, 845, 855, 1197, 1025, 1617, 841, 1395, 1053, 1125, 1629, 1375, 1809, 1899, 661, 1989, 2043, 2061, 1521, 1775, 2133, 2367, 2403, 2421, 2425, 1021, 3105, 3195, 1231, 1249, 3753, 1297, 1307, 2943

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..3398

Example

See A396305.

Mathematica

Block[{c, j, k, m, r, s, t, w, nn, rad},
  nn = 3000; c[_] := False; r = 1; s = 1; t = {};
  rad[n_] := rad[n] = Times @@ FactorInteger[n][[All, 1]];
  Reap[ Do[w = GCD[r, s]; m = r/w; k = m;
    While[Or[c[k], ! CoprimeQ[w, k] ], k += m]; c[k] = True;
    s = r; r = rad[k];
    If[CoprimeQ[s, r], If[Length[t] == 4, Sow[Last[t] ] ]; t = {k},
    AppendTo[t, k] ], {i, nn}] ][[-1, 1]] ] (* Michael De Vlieger, Jun 16 2026 *)

Crossrefs

Cf. A280864, A283832, A396300, A396301, A396305, A396306.

Sequence in context: A096688 A181431 A249067 * A366420 A124983 A087969

Adjacent sequences: A396304 A396305 A396306 * A396308 A396309 A396310

Keyword

nonn,new

Author

N. J. A. Sloane, Jun 16 2026

Status

approved