A128073 Numbers k such that (3^k + 16^k)/19 is prime.

5, 17, 61, 673, 919, 2089, 86939

Offset

1,1

Comments

All terms are primes.

a(8) > 10^5 - Robert Price, Jun 29 2013

Links

Table of n, a(n) for n=1..7.

Mathematica

k=16; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 100} ]

Prog

(PARI) is(n)=isprime((3^n+16^n)/19) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A007658 (numbers k such that (3^k + 1)/4 is prime).

Cf. A057469 (numbers k such that (3^k + 2^k)/5 is prime).

Cf. A122853 (numbers k such that (3^k + 5^k)/8 is prime).

Cf. A128066, A128067, A128068, A128069, A128070, A128071, A128072, A128074, A128075.

Cf. A059801 (numbers k such that 4^k - 3^k is prime).

Cf. A121877 (numbers k such that (5^k - 3^k)/2 is prime).

Cf. A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.

Sequence in context: A273836 A273704 A146444 * A051736 A301560 A099528

Adjacent sequences: A128070 A128071 A128072 * A128074 A128075 A128076

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 14 2007

Extensions

a(5) from Alexander Adamchuk, Feb 14 2007

a(6) and a(7) from Robert Price, Jun 29 2013

Status

approved