OFFSET
1,1
COMMENTS
Integers of the form m^k + 1 for integers m, k >= 2.
REFERENCES
Steven R. Finch, Mathematical Constants, Cambridge University Press, 2003, Section 2.6, p. 113.
LINKS
Vsevolod F. Lev, Re: The sequence of 'perfect' powers, Number Theory List, May 21, 2002.
FORMULA
Sum_{n>=1} 1/a(n) = Pi^2/3 - 5/2 (Lev, 2002). - Amiram Eldar, Oct 15 2020
EXAMPLE
a(1) = 2^2 + 1; a(2) = 2^3 + 1; a(3) = 3^2 + 1; a(4) = 2^4 + 1.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jonathan Vos Post, Sep 15 2012
STATUS
approved