A204897 a(n) = (p(n)-q(n))/n, where (p(n), q(n)) is the least pair of primes for which n divides p(n)-q(n).

1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 2, 1, 1

Offset: 1

Author

Clark Kimberling, Jan 20 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A204892.

It seems that a(A007921(n)) = 2 for all n. - Antti Karttunen, Oct 09 2018

Examples

			(3-2)/1=1
(5-3)/2=1
(5-2)/3=1
(7-3)/4=1
(7-2)/5=1
(11-5)/6=1
(17-3)/7=2
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..12000

Crossrefs

Cf. A007921, A204892, A204896, A000040.

Programs

Mathematica

(See the program at A204892.)

PARI

A204897(n) = { my(d); forprime(p=3,oo, forprime(q=2,p-1,if(!((d=(p-q))%n),return(d/n),if(dAntti Karttunen, Oct 09 2018

Extensions

More terms from Antti Karttunen, Oct 09 2018