

A080902


a(1)=1, a(n)=a(n1)+2 if (n and n+3 are in the sequence), a(n)=a(n1)+3 otherwise.


3



1, 4, 7, 9, 12, 15, 18, 21, 23, 26, 29, 31, 34, 37, 39, 42, 45, 47, 50, 53, 56, 59, 61, 64, 67, 69, 72, 75, 78, 81, 83, 86, 89, 91, 94, 97, 100, 103, 105, 108, 111, 113, 116, 119, 122, 125, 127, 130, 133, 135, 138, 141, 143, 146, 149, 151, 154, 157
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


LINKS

Ivan Neretin, Table of n, a(n) for n = 1..1000


FORMULA

Conjectured to be asymptotic to r*n, where r=2.72... Is r the largest root of q^23*q+3/4, which is 2.72474487139...?


EXAMPLE

a(9)=a(8)+2 since 9 and 12 are in the sequence.


MATHEMATICA

Fold[Append[#1, #1[[1]] + If[MemberQ[#1, #2] && MemberQ[#1, #2 + 3], 2, 3]] &, {1}, Range[2, 58]] (* Ivan Neretin, Mar 03 2016 *)


CROSSREFS

Sequence in context: A184589 A062458 A180122 * A285210 A310953 A284796
Adjacent sequences: A080899 A080900 A080901 * A080903 A080904 A080905


KEYWORD

nonn


AUTHOR

Benoit Cloitre, Apr 01 2003


EXTENSIONS

Corrected by T. D. Noe, Nov 02 2006


STATUS

approved



