A118912 a(1) = 2; a(n) is greatest prime < a(n-1)^4.

2, 13, 28559, 665230244078823349, 195833931687186822327230545227550596864953022841534058316595001440791433

Offset: 1

Author

Jonathan Vos Post, May 05 2006

Keywords

• easy
• nonn

Comments

Exponent-4 analog of A059785 a(n+1)=prevprime(a(n)^2), with exponent 3 being A118910 a(1) = 2; a(n) is greatest prime < a(n-1)^3.

Examples

			a(1) = 2, by definition.
a(2) = 13 = 2^4 - 3.
a(3) = 28559 = 13^4 - 2.
a(4) = 665230244078823349 = 28559^4 - 12.
a(5) = 195833931687186822327230545227550596864953022841534058316595001440791433 = 665230244078823349^4 - 168.
a(6) is too large to include.
		

Crossrefs

Cf. A001358, A055496, A076656, A006992, A005384, A005385, A118908-A118913.

Programs

Mathematica

NestList[NextPrime[#^4,-1]&,2,5] (* Harvey P. Dale, Feb 18 2025 *)

Formula

a(1) = 2; a(n) is greatest prime < a(n-1)^4.