A081841 a(1)=0, a(n)=a(n-1)+3 if n is already in the sequence, a(n)=a(n-1)+2 otherwise.

0, 2, 4, 7, 9, 11, 14, 16, 19, 21, 24, 26, 28, 31, 33, 36, 38, 40, 43, 45, 48, 50, 52, 55, 57, 60, 62, 65, 67, 69, 72, 74, 77, 79, 81, 84, 86, 89, 91, 94, 96, 98, 101, 103, 106, 108, 110, 113, 115, 118, 120, 123, 125, 127, 130, 132, 135, 137, 139, 142, 144, 147, 149, 151

Offset

1,2

Links

Table of n, a(n) for n=1..64.

Formula

a(1)=0; for n>=1 a(n)=floor(r*n-(4*r-1)/(r+1)) where r=1+sqrt(2)

Crossrefs

Sequence in context: A190004 A182761 A329830 * A299234 A366462 A213273

Adjacent sequences: A081838 A081839 A081840 * A081842 A081843 A081844

Keyword

nonn

Author

Benoit Cloitre, Apr 11 2003

Status

approved