A350628 Number of ways to write 2*n as 3^i (i >= 1) plus a prime.

0, 0, 1, 1, 1, 1, 2, 2, 0, 2, 2, 0, 2, 1, 1, 3, 2, 0, 2, 3, 0, 2, 3, 0, 3, 1, 0, 3, 1, 0, 2, 2, 0, 2, 3, 0, 2, 2, 0, 2, 2, 1, 3, 3, 0, 3, 2, 0, 3, 3, 0, 2, 3, 0, 4, 3, 0, 3, 2, 0, 2, 2, 0, 2, 2, 0, 3, 2, 0, 4, 2, 0, 1, 2, 0, 2, 3, 0, 2, 3, 0, 2, 3, 0, 2, 1, 0, 3, 2, 0, 3, 3, 0, 2, 3

Offset

1,7

Links

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

Maple

f:= proc(n) local i;
 nops(select(isprime, [seq(2*n-3^i, i=1..ilog[3](2*n))]))
end proc:
map(f, [$1..100]); # Robert Israel, Feb 04 2026

Crossrefs

Cf. A006285, A058517, A350629, A350630, A350957, A350958.

Sequence in context: A114700 A353768 A140666 * A202145 A130772 A257076

Adjacent sequences: A350625 A350626 A350627 * A350629 A350630 A350631

Keyword

nonn

Author

N. J. A. Sloane, Feb 05 2022

Status

approved