OFFSET
1,1
COMMENTS
Values of the exponent n are given in A275767, and every exponent (except for the first one) is odd. Consequently, after a(1) = 5, the rightmost digit of each term in this sequence will be 1.
As seen in the link below, a(5) = 2*4^291 - 27 > 3.1658 * 10^175. As a result of the recent extensions to A275767 by Vincenzo Librandi,
a(6) = 2*4^1263 - 27 > 5.0442 * 10^760
a(7) = 2*4^2661 - 27 > 2.4136 * 10^1602
a(8) = 2*4^3165 - 27 > 6.6206 * 10^1905
a(9) > 2*4^5000 - 27 > 3.9901 * 10^3010.
These primes a(m) can be used to generate numbers having abundance 26. The formula a(m)*(a(m)+27)/2 produces some of the terms in A275701.
LINKS
Timothy L. Tiffin, Table of n, a(n) for n = 1..5
D. Alpern, Factorization using the Elliptic Curve Method.
FORMULA
a(m) = 2*4^A275767(m) - 27.
EXAMPLE
MATHEMATICA
Select[2*4^Range[2, 200] - 27, PrimeQ] (* Michael De Vlieger, Aug 08 2016 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Timothy L. Tiffin, Aug 07 2016
STATUS
approved