A081329 Numbers having no representation as sum of two 3-smooth numbers.

1, 23, 46, 47, 53, 61, 69, 71, 77, 79, 92, 94, 95, 101, 103, 106, 107, 115, 119, 121, 122, 125, 127, 133, 138, 139, 141, 142, 143, 149, 151, 154, 157, 158, 159, 161, 167, 169, 173, 175, 179, 181, 183, 184, 185, 187, 188, 190, 191, 197, 199, 202, 203, 205, 206

Offset

1,2

Comments

Complement of A081330.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

A081326(a(n)) = 0.

Example

For all 3-smooth numbers m<23 the greatest prime factor of 23-m is >3: 23-1=2*11, 23-2=3*7, 23-3=4*5, 23-2^2=19, 23-2*3=17, 23-2^3=3*5, 23-3^2=2*7, 23-3*2^2=11, 23-2^4=7, 23-2*3^2=5, therefore 23 is a term.

Mathematica

max = 300; Complement[Range[max], Table[2^i*3^j + 2^k*3^l, {i, 0, Log[2, max] // Ceiling}, {j, 0, Log[3, max] // Ceiling}, {k, 0, Log[2, max] // Ceiling}, {l, 0, Log[3, max] // Ceiling}] // Flatten // Union // Select[#, # <= max& ]& ] (* Jean-François Alcover, Sep 10 2017 *)

Crossrefs

Cf. A003586, A081326, A081330.

Sequence in context: A122041 A266706 A040506 * A323046 A025022 A260750

Adjacent sequences: A081326 A081327 A081328 * A081330 A081331 A081332

Keyword

nonn

Author

Reinhard Zumkeller, Mar 19 2003

Status

approved