A099482 Semiprimes of the form 2^k - k^2.

1927, 8023, 32543, 2096711, 8388079, 137438952103, 549755812367, 2199023253871, 8796093020359, 140737488353119, 562949953418911, 36028797018960943, 147573952589676408439, 37778931862957161703943

Offset

1,1

Links

Hugo Pfoertner, Table of n, a(n) for n = 1..36

Dario Alpern, Factorization using the Elliptic Curve Method.

Example

a(2) = 8023 because 8023 = 71*113 = 2^13 - 13^2 = 2^A099481(2) - A099481(2)^2.

Mathematica

Select[Table[2^n - n^2, {n, 100}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 21 2012 *)

Crossrefs

Cf. A024012 2^n-n^2, A099481 2^k-k^2 is a semiprime, A072180 2^k-k^2 is prime, A075896 primes of the form 2^k-k^2.

Sequence in context: A283949 A133301 A258841 * A253337 A200435 A252108

Adjacent sequences: A099479 A099480 A099481 * A099483 A099484 A099485

Keyword

nonn

Author

Hugo Pfoertner, Oct 18 2004

Status

approved