A100689 a(n) = prime(n) * 4^prime(n) - 1.

31, 191, 5119, 114687, 46137343, 872415231, 292057776127, 5222680231935, 1618481116086271, 8358680908399640575, 142962266571249025023, 698910239464707491627007, 198263834416799184651812863, 3326963855579459488791396351, 930930909542605966724141416447

Offset: 1

Author

Parthasarathy Nambi, Dec 07 2004

Keywords

• nonn

Examples

			a(1) = 2*4^2 - 1 = 31.
		

Programs

Magma

[NthPrime(n)*4^NthPrime(n) - 1: n in [1..20]]; // Vincenzo Librandi, Aug 27 2015

Mathematica

Do[Print[Prime[n]*4^(Prime[n]) - 1], {n, 1, 20}] (* Stefan Steinerberger, Feb 15 2006 *)
# 4^#-1&/@Prime[Range[20]] (* Harvey P. Dale, Dec 06 2012 *)

PARI

vector(20, n, p=prime(n); p*4^p - 1) \\ Michel Marcus, Aug 27 2015

Formula

a(n) = A060416(prime(n)) = A060416(A000040(n)). - Michel Marcus, Aug 27 2015

Extensions

More terms from Stefan Steinerberger, Feb 15 2006

a(14)-a(15) from Vincenzo Librandi, Aug 27 2015