OFFSET
3,1
COMMENTS
All prime factors of 2^p - p^2 are congruent to 1 or 7 (mod 8). (See A001132.) - Robert G. Wilson v, Mar 14 2022
REFERENCES
E.-B. Escott, Note #1642, L'Intermédiaire des Mathématiciens, 8 (1901), page 12.
LINKS
Amiram Eldar, Table of n, a(n) for n = 3..95
Robert G. Wilson v, Factorization of 2^p - p^2 for n = 3..120
FORMULA
MAPLE
a:= n-> max(numtheory[factorset]((p-> 2^p-p^2)(ithprime(n)))):
seq(a(n), n=3..27); # Alois P. Heinz, Mar 03 2022
MATHEMATICA
a[n_] := FactorInteger[2^(p = Prime[n]) - p^2][[-1, 1]]; Array[a, 25, 3] (* Amiram Eldar, Mar 03 2022 *)
PROG
(PARI) a(n) = my(p=prime(n)); vecmax(factor(2^p - p^2)[, 1]); \\ Michel Marcus, Mar 03 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 02 2022
STATUS
approved