A323049 Numbers that are neither 5-smooth nor a sum of two 5-smooth numbers.

71, 119, 142, 191, 211, 213, 223, 238, 239, 284, 299, 311, 319, 355, 357, 359, 367, 373, 382, 397, 419, 422, 426, 431, 446, 461, 463, 467, 473, 476, 478, 479, 497, 523, 529, 547, 551, 553, 559, 568, 569, 571, 573, 583, 589, 595, 598, 599, 607, 613, 617, 619, 622, 623, 638, 639, 659, 669, 671, 703, 709, 710, 713, 714

Offset

1,1

Comments

Complementary set of (A323048).

Also numbers k such that at least three five-smooth numbers are needed to sum to k. - David A. Corneth, Jan 04 2019

Contains all k == 71 or 119 (mod 120). - Robert Israel, Apr 02 2019

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

N:= 1000: # to get all terms <= N
V:= {seq(seq(seq(2^a*3^b*5^c, a = 0 .. floor(log[2](N/3^b/5^c))), b = 0 .. floor(log[3](N/5^c))), c=0..floor(log[5](N)))}:
S:= {$1..N} minus V minus {seq(seq(V[i]+V[j], i=1..j), j=1..nops(V))}:
A:= sort(convert(S, list)): # Robert Israel, Apr 02 2019

Mathematica

f[n_] := Union@Flatten@Table[2^a*3^b*5^c, {a, 0, Log2[n]}, {b, 0, Log[3, n/2^a]}, {c, 0, Log[5, n/(2^a*3^b)]}]; b = Block[{nn = 800, s}, s = f[nn]; {0, 1}~Join~
   Select[Union@Flatten@Outer[Plus, s, s], # <= nn &]];
Complement[Range[800], b]

Crossrefs

Cf. A003586, A051037, A323048.

Similar to A323046 (for 3-smooth numbers).

Sequence in context: A243888 A033246 A141879 * A026063 A244167 A115395

Adjacent sequences: A323046 A323047 A323048 * A323050 A323051 A323052

Keyword

nonn

Author

Carlos Alves, Jan 03 2019

Status

approved