A038702 Prime(n)^2 mod prime(n-1).

1, 1, 4, 2, 4, 3, 4, 16, 13, 4, 5, 16, 4, 16, 36, 36, 4, 36, 16, 4, 36, 16, 36, 64, 16, 4, 16, 4, 16, 83, 16, 36, 4, 100, 4, 36, 36, 16, 36, 36, 4, 100, 4, 16, 4, 144, 144, 16, 4, 16, 36, 4, 100, 36, 36, 36, 4, 36, 16, 4, 100, 196, 16, 4

Offset: 2

Author

Neil Fernandez, May 01 2000

Keywords

• nonn
• easy

Comments

a(n+1) = n-th prime gap squared mod the n-th prime = A076821(n) mod A000040(n). Probably a(n) = A076821(n+1) for n > 31. This holds up to 4 * 10^18. - Charles R Greathouse IV, Apr 17 2012

Examples

			To get a(4): square the fourth prime to get 7^2 = 49. The remainder when this is divided by the third prime, 5, is 4. So a(3) = 4.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 2..10000

Crossrefs

Cf. A038703.

Programs

Maple

A038702 := proc(n)
    modp( ithprime(n)^2,ithprime(n-1)) ;
end proc: # R. J. Mathar, Jan 09 2015

Mathematica

Table[Mod[Prime[n+1]^2,Prime[n]],{n,5!}] (* Vladimir Joseph Stephan Orlovsky, Apr 26 2010 *)
Table[PowerMod[Prime[n],2,Prime[n-1]],{n,2,70}] (* Harvey P. Dale, Mar 22 2012 *)

PARI

a(n)=prime(n)^2%prime(n-1) \\ Charles R Greathouse IV, Apr 17 2012