A219761 a(1) = 1; for n>1, a(n) = smallest integer > a(n-1) such that a(n)*a(n-i)+1 is prime for all 0 <= i <= n-1.

1, 2, 6, 156, 4260, 117306, 160650, 13937550, 32742516, 3306719796, 7746764190

Offset: 1

Author

N. J. A. Sloane, Dec 01 2012

Keywords

• nonn
• more

Examples

			After a(1)=1, a(2)=2, a(3)=6, we want the smallest m>6 such that 1+m, 1+2m, 1+6m and 1+m^2 are all prime: this is m = 156 = a(4).
		

References

• Rainer Rosenthal, Posting to Sequence Fans Mailing List, Nov 30 2012.

Crossrefs

Cf. A034881, A081942, A093483.

Programs

Mathematica

f[a_List] := Block[{m = a, k = a[[-1]] + 6}, While[ Union@ PrimeQ[k*Join[m, {k}] + 1] != {True}, k += 6]; k]; s = {1, 2, 6}; Do[ Print[{n, a = f[s]}]; s = Append[s, a], {n, 4, 9}] (* Robert G. Wilson v, Dec 03 2012 *)

Extensions

a(8) and a(9) from Robert G. Wilson v, Dec 03 2012

a(10) and a(11) from Robert G. Wilson v, Dec 04 2012