A083055 a(n) = cardinality{ k<=n / A083054(k)=1}.

1, 1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 9, 9, 10, 10, 10, 10, 10, 11, 11, 12, 12, 12, 13, 13, 14, 14, 14, 14, 14, 15, 15, 16, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 18, 19, 19, 20, 20, 20, 21, 21, 22, 22, 22, 22, 22, 23, 23, 24, 24, 24, 24, 24, 25, 25

Offset

1,6

Links

Table of n, a(n) for n=1..78.

Boris Gourevitch, Graph of A083057

Formula

a(n) = n/3 + O(n) (it seems O(n) could be replaced with O(log(n))).

Prog

(PARI) {a(n)=if(n<1, 0, sum(k=1, n, sqrtint(3*k^2)-3*sqrtint(k^2\3)==1))} /* Michael Somos, Aug 31 2006 */

Crossrefs

Cf. A083038, A083054, A083056, A083057.

Sequence in context: A302128 A054071 A028827 * A231149 A195072 A121828

Adjacent sequences: A083052 A083053 A083054 * A083056 A083057 A083058

Keyword

nonn

Author

Benoit Cloitre, Apr 18 2003

Status

approved