A098972 a(0) = 1; for n > 0, a(n) = 2*a(floor(n/2)) + 3*a(floor(n/3)).

1, 5, 13, 25, 41, 41, 89, 89, 121, 157, 157, 157, 301, 301, 301, 301, 365, 365, 581, 581, 581, 581, 581, 581, 965, 965, 965, 1073, 1073, 1073, 1073, 1073, 1201, 1201, 1201, 1201, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 2065, 3025

Offset: 0

Author

Benoit Cloitre, Oct 23 2004

Keywords

• nonn

Comments

a(n) > a(n-1) iff n is a 3-smooth number.

Links

• Amiram Eldar, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A003586, A007731, A065333.

Programs

Mathematica

a[0] = 1; a[n_] := a[n] = 2*a[Floor[n/2]] + 3*a[Floor[n/3]]; Array[a, 50, 0] (* Amiram Eldar, Jul 13 2023 *)

PARI

a(n)=if(n<1,1,a(floor(n/2))*2+3*a(floor(n/3)))

Formula

sign(a(n+1)-a(n)) = A065333(n+1).