A093701 a(n) = smallest m>a(n-1) such that 1+m*n is prime, a(1) = 1.

1, 2, 4, 7, 8, 10, 16, 17, 18, 19, 30, 31, 34, 35, 36, 37, 38, 41, 58, 59, 62, 64, 72, 73, 76, 77, 80, 81, 84, 85, 88, 95, 96, 97, 102, 103, 106, 111, 114, 118, 122, 123, 124, 125, 130, 132, 134, 135, 138, 140, 142, 144, 150, 152, 156, 158, 164, 166, 174, 175

Offset: 1

Author

Reinhard Zumkeller, Apr 10 2004

Keywords

• nonn

Comments

A093702(n) = 1+a(n)*n.

Examples

			For n=3: we have a(2)=2, so we want the smallest number m > 2 such that n*m+1 = 3*m+1 is prime. m=3 fails but m=4 works, so a(3) = m = 4. - _N. J. A. Sloane_, Dec 13 2018
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A013632, A093702.

Note that A081942 is a related but distinct sequence.

Programs

Mathematica

nxt[{n_,a_}]:=Module[{m=a+1},While[!PrimeQ[m(n+1)+1],m++];{n+1,m}]; NestList[ nxt,{1,1},60][[All,2]] (* Harvey P. Dale, Dec 13 2018 *)