A080725 a(1) = 2; for n>1, a(n) is taken to be the smallest positive integer greater than a(n-1) which is consistent with the condition "n is a member of the sequence if and only if a(n) == 1 mod 3".

2, 4, 5, 7, 10, 11, 13, 14, 15, 16, 19, 20, 22, 25, 28, 31, 32, 33, 34, 37, 38, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 52, 55, 58, 59, 60, 61, 64, 65, 67, 70, 73, 76, 79, 82, 85, 88, 91, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 106, 109, 112, 113, 114, 115, 118, 119, 121

Offset

1,1

Links

Table of n, a(n) for n=1..67.

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2.

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence (math.NT/0305308)

Index entries for sequences of the a(a(n)) = 2n family

Formula

a(a(n)) = 3*n+1, n >= 1.

Prog

(PARI) {a=2; m=[2]; for(n=2, 68, print1(a, ", "); a=a+1; if(m[1]==n, while(a%3!=1, a++); m=if(length(m)==1, [], vecextract(m, "2..")), if(a%3==1, a++)); m=concat(m, a))}

Crossrefs

Cf. A079000, A080720, ...

Sequence in context: A231014 A231009 A133254 * A182337 A024914 A189636

Adjacent sequences: A080722 A080723 A080724 * A080726 A080727 A080728

Keyword

nonn,easy

Author

N. J. A. Sloane, Mar 08 2003

Extensions

More terms and PARI code from Klaus Brockhaus, Mar 08 2003

Status

approved