A063486 a(n) = 2^(2^n) + 5.

7, 9, 21, 261, 65541, 4294967301, 18446744073709551621, 340282366920938463463374607431768211461, 115792089237316195423570985008687907853269984665640564039457584007913129639941

Offset: 0

Author

Jason Earls, Jul 28 2001

Keywords

• easy
• nonn

References

• D. M. Burton, Elementary Number Theory, Allyn and Bacon Inc., Boston, MA, 1976, p. 238.
• James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, Example 5.1 on page 153.

Links

• Harry J. Smith, Table of n, a(n) for n=0..11
• Tigran Hakobyan, On the unboundedness of common divisors of distinct terms of the sequence a(n)=2^2^n+d for d>1, arXiv:1601.04946 [math.NT], 2016.

Crossrefs

Cf. A000215, A001146, A130729, A130730.

Programs

Mathematica

2^2^Range[0, 10] + 5 (* Paolo Xausa, Apr 17 2024 *)

PARI

for(n=0,8,print1(2^(2^n)+5, ", "))

PARI

{ for (n=0, 11, write("b063486.txt", n, " ", 2^(2^n) + 5) ) } \\ Harry J. Smith, Aug 23 2009

SageMath

[2**2**n + 5 for n in (0..8)] # Stefano Spezia, Jul 20 2025