A180417 a(n) = (A000111(2^n) - 1) / 2^n.

0, 0, 1, 173, 1211969509, 5547480986860602794895774677, 708720364531529518355420122993246286974247836241724513772950684967495246261

Offset

0,4

Comments

The definition yields integers according to the formula in A000111.

The next term a(7) is too large to include. - N. J. A. Sloane, Mar 14 2011

Links

Alois P. Heinz, Table of n, a(n) for n = 0..8

Mathematica

t = Range[0, 65]! CoefficientList[ Series[ Sec@x + Tan@x, {x, 0, 65}], x]; f[n_] := (Rest[t][[2^n]] - 1)/2^n; Array[f, 7, 0] (* Robert G. Wilson v, Sep 04 2010 *)

Prog

(Python)
from sympy import euler
def A180417(n): return euler(1<<n)-1>>n if n > 1 else 0 # Chai Wah Wu, Apr 18 2023

Crossrefs

Cf. A000079, A000111.

Sequence in context: A185701 A138267 A096709 * A351375 A160660 A025390

Adjacent sequences: A180414 A180415 A180416 * A180418 A180419 A180420

Keyword

nonn

Author

Vladimir Shevelev, Sep 03 2010

Extensions

Two more terms from R. J. Mathar, Sep 19 2010

a(5) and a(6) from Robert G. Wilson v, Sep 04 2010

Status

approved