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A346676 Numbers expressible as 2^x + 3^y where both x and y are positive integers. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms have the form 6k +- 1.

LINKS

Table of n, a(n) for n=1..55.

FORMULA

{ A004050 } minus { A000079, A000244 }.

PROG

(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))

print(aupto(1242)) # Michael S. Branicky, Jul 29 2021

CROSSREFS

Cf. A000079, A000244, A004050.

Sequence in context: A216524 A128824 A098420 * A309726 A093495 A093496

Adjacent sequences: A346673 A346674 A346675 * A346677 A346678 A346679

KEYWORD

nonn

AUTHOR

Keith Backman, Jul 28 2021

STATUS

approved

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Last modified January 29 17:53 EST 2023. Contains 359925 sequences. (Running on oeis4.)