A081840 a(1)=0, a(n)=a(n-1)+3 if n is already in the sequence, a(n)=a(n-1)+4 otherwise.

0, 4, 8, 11, 15, 19, 23, 26, 30, 34, 37, 41, 45, 49, 52, 56, 60, 64, 67, 71, 75, 79, 82, 86, 90, 93, 97, 101, 105, 108, 112, 116, 120, 123, 127, 131, 134, 138, 142, 146, 149, 153, 157, 161, 164, 168, 172, 176, 179, 183, 187, 190, 194, 198, 202, 205, 209, 213, 217

Offset

1,2

Links

Table of n, a(n) for n=1..59.

Formula

a(n) = floor(r*n-(2*r+1)/(r-1)) where r = 2+sqrt(3).

Crossrefs

Sequence in context: A047346 A198270 A214971 * A311050 A311051 A311052

Adjacent sequences: A081837 A081838 A081839 * A081841 A081842 A081843

Keyword

nonn

Author

Benoit Cloitre, Apr 11 2003

Status

approved