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A346676
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Numbers expressible as 2^x + 3^y where both x and y are positive integers.
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0
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5, 7, 11, 13, 17, 19, 25, 29, 31, 35, 41, 43, 59, 67, 73, 83, 85, 89, 91, 97, 113, 131, 137, 145, 155, 209, 245, 247, 251, 259, 265, 275, 283, 307, 337, 371, 499, 515, 521, 539, 593, 731, 733, 737, 745, 755, 761, 793, 857, 985, 1027, 1033, 1051, 1105, 1241
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OFFSET
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1,1
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COMMENTS
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All terms have the form 6k +- 1.
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LINKS
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FORMULA
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PROG
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(PARI) f(x, y) = 2^x + 3^y;
lista(nn) = select(x->(x<=nn), setbinop(f, [1..logint(nn, 2)], [1..logint(nn, 3)])); \\ Michel Marcus, Jul 29 2021
(Python)
def aupto(lim):
s, pow3 = set(), 3
while pow3 < lim:
for j in range(1, (lim-pow3).bit_length()):
s.add(2**j + pow3)
pow3 *= 3
return sorted(set(s))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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