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A088123

Let f(n,x) = 1 + 2x + 3x^2 + 5x^3 + 7x^4 + ... + prime(n)*x^n; a(n) = smallest value of x such that f(n,x) is a prime, or 0 if no such prime exists.

1, 2, 1, 6, 1, 6, 1, 8, 1, 74, 6, 6, 1, 2, 11, 102, 20, 88, 1, 52, 10, 18, 2, 56, 1, 26, 37, 216, 1, 78, 1, 28, 21, 160, 3, 276, 30, 1542, 42, 598, 20, 20, 333, 186, 8, 82, 11, 90, 1, 246, 1, 240, 83, 58, 9, 76, 1, 16, 21, 700, 60, 10, 87, 250, 62, 406, 2, 502, 140, 186, 1293, 578

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OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

EXAMPLE

a(4) = 6 as, A088122(4) = 10273 = f(4,6).

MATHEMATICA

Table[Clear[x, n, eq]; eq=Total[Table[Prime[n]x^n, {n, t}]]+1; x=1; While[ !PrimeQ[ eq], x++]; x, {t, 80}] (* Harvey P. Dale, Apr 27 2013 *)

CROSSREFS

Cf. A088122.

Sequence in context: A382512 A328580 A362784 * A050932 A366573 A366570