A144675 Numbers n such that A090831(n) is prime.

1, 2, 6, 8, 10, 242

Offset

1,2

Comments

No further terms up to n=2540 (A090831(2540) ~ 10^7400). A090831(242) is a proved prime (in spite of the given PARI code).

Obviously all terms beyond the first must be even, so one might as well consider a(n)/2 = 1,3,4,5,121,...

Links

Table of n, a(n) for n=1..6.

Prog

(PARI) print1(1); forstep( n=2, 3000, 2, /* n%10|print1([n]); */ ispseudoprime( sum( i=1, n, prime(i)^(n+1-i))) & print1(", "n))

Crossrefs

Sequence in context: A185078 A214402 A166064 * A088417 A050880 A182424

Adjacent sequences: A144672 A144673 A144674 * A144676 A144677 A144678

Keyword

nonn,more,hard

Author

M. F. Hasler, Feb 02 2009, Feb 16 2009

Status

approved