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A323048 Sums of no more than two 5-smooth numbers. 2
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Sequence includes 5-smooth numbers (A051037).
Numbers that are of the form (2^i * 3^j * 5^k)*a + (2^m * 3^n * 5^p)*b, with i,j,k,m,n,p >= 0, and a,b = 0 or 1. The first number excluded is 71. The numbers excluded are in A323049.
LINKS
EXAMPLE
70 = 2*2*3*5 + 2*5, 72 = 2*2*2*3*3 = 2*2*3*5 + 2*2*3, but 71 is not in the sequence.
MATHEMATICA
S5 = Join[{0}, Select[Range[500], FactorInteger[#][[-1, 1]] <= 5 &]];
Union@Flatten@Outer[Plus, S5, S5]
(* more efficient code by Michael De Vlieger *)
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)]}]; Block[{nn = 500, s}, s = f[nn]; {0, 1}~Join~
Select[Union@Flatten@Outer[Plus, s, s], # <= nn &]]
CROSSREFS
Cf. A051037, A323049 (complementary sequence).
Sequence in context: A258069 A361374 A090108 * A090109 A153671 A090107
KEYWORD
nonn
AUTHOR
Carlos Alves, Jan 03 2019
EXTENSIONS
Name edited by Jianing Song, Jun 11 2019
STATUS
approved

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Last modified March 28 17:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)