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A186688 Semiprimes of the form n^4 + 1. 2
82, 626, 2402, 4097, 10001, 14642, 20737, 28562, 38417, 83522, 104977, 194482, 234257, 279842, 456977, 707282, 810001, 1048577, 1500626, 1679617, 2085137, 2313442, 2560001, 3111697, 6250001, 7311617, 10556002, 11316497, 13845842, 14776337, 17850626, 21381377, 25411682 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

4097 is a member because 4097 = 8^4 + 1 = 17*241.

MATHEMATICA

semiPrimeQ[n_] := Total[FactorInteger[n]][[2]] == 2; Select[ Range[200]^4

  +1, semiPrimeQ]

Select[Table[n^4 + 1, {n, 80}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 22 2012 *)

PROG

(MAGMA) IsSemiprime:= func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [1..75] | IsSemiprime(s) where s is n^4 + 1]; // Vincenzo Librandi, Sep 22 2012

CROSSREFS

Cf. A144255.

Sequence in context: A282773 A182277 A342832 * A002309 A128959 A305682

Adjacent sequences:  A186685 A186686 A186687 * A186689 A186690 A186691

KEYWORD

nonn,easy

AUTHOR

Michel Lagneau, Feb 25 2011

STATUS

approved

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Last modified August 16 11:28 EDT 2022. Contains 356168 sequences. (Running on oeis4.)