A396385 a(n) = r(n,n), where r(1,k)=f(k)=floor(k*c), r(n,k)=f(r(n-1,k)), c=3/2.

1, 4, 9, 19, 33, 63, 109, 202, 316, 549, 913, 1531, 2398, 3937, 6246, 10390, 15898, 26151, 40965, 65409, 100878, 160065, 252193, 399403, 611158, 969691, 1507965, 2362204, 3632062, 5657635, 8725657, 13779540, 20767725, 32721003, 50139508, 77731542, 118943142

Offset

1,2

Comments

a(n + 1)/a(n) approaches c erratically.

Links

Table of n, a(n) for n=1..37.

Example

(a(n)) is the main diagonal of the rectangular array (r(n,k)), having corner
1   3    4    6    7    9
1   4    6    9   10   13
1   6    9   13   15   19
1   9   13   19   22   28

Mathematica

c = 3/2; f[k_] := f[k] = Floor[c*k];
r[1, k_] := f[k]; r[n_, k_] := r[n, k] = f[r[n - 1, k]];
Table[r[n, n], {n, 1, 100}]

Crossrefs

Cf. A353220, A396386, A396390.

Sequence in context: A009856 A009920 A179862 * A008036 A009863 A301249

Adjacent sequences: A396382 A396383 A396384 * A396386 A396387 A396388

Keyword

nonn

Author

Clark Kimberling, May 24 2026

Status

approved