A020707 Pisot sequences E(4,8), L(4,8), P(4,8), T(4,8).

4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648, 4294967296, 8589934592

Offset: 0

Author

David W. Wilson

Keywords

• nonn
• easy

Comments

Subsequence of A051916. - Reinhard Zumkeller, Mar 20 2010

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..238
• Tanya Khovanova, Recursive Sequences
• Index to divisibility sequences
• Index entries for linear recurrences with constant coefficients, signature (2).

Crossrefs

Subsequence of A000079. See A008776 for definitions of Pisot sequences.

Cf. A051916.

Programs

Magma

[2^(n+2): n in [0..40]]; // Vincenzo Librandi, Apr 28 2011

Mathematica

2^(Range[0, 50] + 2) (* Vladimir Joseph Stephan Orlovsky, Jun 09 2011 *)

PARI

a(n)=4<Charles R Greathouse IV, Apr 08 2012

Python

def A020707(n): return 1<Chai Wah Wu, Apr 02 2025

Formula

a(n) = 2^(n+2).

a(n) = 2*a(n-1).

G.f.: 4/(1-2*x). - Philippe Deléham, Nov 23 2008

E.g.f.: 4*exp(2*x). - Stefano Spezia, May 15 2021