A114889 a(1)=1 and, for n>1, a(n) is the smallest integer greater than a(n-1) such that a(n)+a(i) is not a power of 3, for i=1,..., n-1.

1, 3, 4, 7, 9, 10, 11, 12, 13, 19, 21, 22, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 55, 57, 58, 61, 63, 64, 65, 66, 67, 73, 75, 76, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108

Offset

1,2

Comments

The differences of {a(n)}, together with a conjectured formula for them, is given in A114890.

Links

Table of n, a(n) for n=1..68.

Example

Given that a(1)=1, a(2)=3 and a(3)=4, we find that a(4)>5 since 5+4=9 and a(4)>6 since 6+3=9. But none of 7+1, 7+3, or 7+4 is a power of 3, so a(4)=7.

Crossrefs

Cf. A005652, A114890.

Sequence in context: A324495 A087276 A138225 * A174659 A242423 A010444

Adjacent sequences: A114886 A114887 A114888 * A114890 A114891 A114892

Keyword

nonn

Author

John W. Layman, Jan 04 2006

Status

approved