A156021 Numbers k such that k^1 + k^2 + k^3 + k^4 -+ 1 are twin primes.

1, 2, 12, 30, 44, 50, 63, 74, 110, 165, 177, 222, 239, 254, 327, 492, 519, 804, 942, 954, 1007, 1343, 1352, 1520, 1770, 2375, 2450, 2658, 2795, 2945, 2994, 3075, 3332, 3527, 3548, 3803, 3915, 3935, 4025, 4653, 4704, 4785, 4808, 4862, 5270, 5310, 5364, 5370

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

2 is a term since 2 + 2^2 + 2^3 + 2^4 - 1 = 29 and 2 + 2^2 + 2^3 + 2^4 + 1 = 31 are twin primes.

Mathematica

lst={}; Do[p=(n^1+n^2+n^3+n^4); If[PrimeQ[p-1]&&PrimeQ[p+1], AppendTo[lst, n]], {n, 8!}]; lst

Prog

(Magma) [n: n in [1..6*10^3] | IsPrime(n^4+n^3+n^2+n-1) and IsPrime(n^4+n^3+n^2+n+1)]; // Vincenzo Librandi, Dec 26 2015

Crossrefs

Cf. A125964, A156018.

Sequence in context: A215784 A061780 A249411 * A067348 A002939 A118239

Adjacent sequences: A156018 A156019 A156020 * A156022 A156023 A156024

Keyword

nonn,easy

Author

Vladimir Joseph Stephan Orlovsky, Feb 01 2009

Status

approved