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A115404 Numbers n such that n^4+1 is a 4-almost prime (product of four primes). 1
43, 59, 77, 79, 83, 85, 95, 111, 127, 137, 147, 155, 178, 179, 185, 202, 221, 223, 227, 229, 233, 239, 241, 247, 249, 253, 261, 263, 270, 271, 273, 285, 287, 297, 314, 331, 338, 341, 342, 357, 359, 387, 389, 393, 395, 401, 408, 413, 421, 427, 433, 435, 437 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

n^4+1=p*q*r*s where p, q, r, s are primes (not necessarily distinct).

EXAMPLE

43 is OK because 43^4+1=3418802=2*17*193*521 (product of four primes).

MATHEMATICA

Select[Range[500], Sum[FactorInteger[ #^4 + 1][[i]][[2]], {i, 1, Length[FactorInteger[ #^4 + 1]]}] == 4 &] (* Stefan Steinerberger, Mar 09 2006 *)

PROG

(PARI) is(n)=bigomega(n^4+1)==4 \\ Charles R Greathouse IV, Oct 11 2013

CROSSREFS

Cf. A014613 = 4-almost primes.

Sequence in context: A127880 A078132 A201613 * A033223 A215538 A235149

Adjacent sequences:  A115401 A115402 A115403 * A115405 A115406 A115407

KEYWORD

nonn

AUTHOR

Zak Seidov, Mar 08 2006

STATUS

approved

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Last modified October 18 04:57 EDT 2019. Contains 328145 sequences. (Running on oeis4.)