A081332 Numbers having a unique partition into two 3-smooth numbers.

2, 3, 29, 31, 37, 41, 43, 49, 55, 58, 59, 62, 65, 67, 74, 83, 85, 86, 87, 89, 91, 93, 98, 109, 110, 111, 113, 116, 118, 123, 124, 130, 131, 134, 137, 147, 148, 155, 163, 165, 166, 170, 172, 174, 177, 178, 182, 186, 193, 195, 196, 201, 209, 217, 218, 220, 222, 226

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Formula

A081326(a(n)) = 1.

Mathematica

nmax = 1000;
S = Select[Range[nmax], Max[FactorInteger[#][[All, 1]]] <= 3 &];
P[n_] := IntegerPartitions[n, {2}, TakeWhile[S, # < n &]];
selQ[n_] := Length[P[n]] == 1;
Select[Range[nmax], selQ] (* Jean-François Alcover, Oct 14 2021 *)

Crossrefs

Cf. A003586, A081326, A081333, A081330.

Sequence in context: A351693 A324941 A028868 * A106868 A098419 A041193

Adjacent sequences: A081329 A081330 A081331 * A081333 A081334 A081335

Keyword

nonn

Author

Reinhard Zumkeller, Mar 19 2003

Status

approved