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A070156
Numbers k such that k-1, k+1, k^2+1 and k^4+1 are all prime numbers.
6
4, 6, 180, 3390, 18060, 19380, 34500, 92220, 92640, 96180, 114660, 127680, 133980, 140760, 159630, 161880, 172170, 207480, 254280, 255840, 263820, 296910, 309780, 378570, 380880, 397590, 408690, 422880, 432660, 440550, 511170, 540390, 572940
OFFSET
1,1
LINKS
EXAMPLE
For n = 6: 5, 7, 37, 1297 are all primes.
MATHEMATICA
Do[s=n; If[PrimeQ[n-1]&&PrimeQ[n+1]&&PrimeQ[1+n^2] &&PrimeQ[1+n^4], Print[n]], {n, 1, 1000000}]
PROG
(PARI) is(k) = isprime(k-1) && isprime(k+1) && isprime(k^2+1) && isprime(k^4+1); \\ Amiram Eldar, Jun 21 2024
CROSSREFS
Subsequence of A070155.
Cf. A001359.
Sequence in context: A197882 A074124 A303161 * A298147 A081970 A076098
KEYWORD
easy,nonn
AUTHOR
Labos Elemer, Apr 23 2002
EXTENSIONS
Offset corrected by Amiram Eldar, Jun 21 2024
STATUS
approved