A069564 a(1) = 2; a(n) = k*a(n-1) + 1 is a multiple of n-th prime with k > 1.

2, 9, 55, 441, 4411, 13234, 26469, 238222, 476445, 3335116, 60032089, 1680898493, 15128086438, 605123457521, 6051234575211, 90768518628166

Offset

1,1

Comments

a(16) is divisible by the 17th prime, so there can be no a(17). - Robert Israel, Feb 23 2017

Links

Table of n, a(n) for n=1..16.

Example

After a(2) = 9 we have a(3) = 6*9 + 1 = 55 since this is smallest such number divisible by the third prime 5.

Maple

a[1]:= 2:
for n from 2 to 16 do
  v:= chrem([1, 0], [a[n-1], ithprime(n)]);
  if v = a[n-1]+1 then a[n]:= v + a[n-1]*ithprime(n) else a[n]:= v fi
od:
seq(a[i], i=1..16); # Robert Israel, Feb 23 2017

Mathematica

a = 1; Do[k = 2; While[ !IntegerQ[(k*a + 1)/Prime[n]], k++ ]; a = (k*a + 1); Print[a], {n, 1, 16}]

Crossrefs

Cf. A069563.

Sequence in context: A036074 A231172 A009363 * A109366 A303914 A241457

Adjacent sequences: A069561 A069562 A069563 * A069565 A069566 A069567

Keyword

nonn,fini,full

Author

Amarnath Murthy, Mar 23 2002

Extensions

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jul 02 2002

More terms from Robert G. Wilson v, Oct 10 2002

Status

approved