0,3

a(5) = 3175 042373 780336 892901 667920 556557 182493 442088 021222 004926 225128 381629 943118 937129 098831 435345 716937 405655 305190 657814 877412 786176 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000. - Jonathan Vos Post (jvospost2(AT)yahoo.com), Dec 09 2004

Note that, by analogy with factorial primes, subfactorial primes, superfactorial primes, and hyperfactorial primes, that if a(n)+1 or a(n)-1 is prime, it should be called an ultrafactorial prime. These begin: a(0)+1 = a(1)+1 = 2, a(2)-1 = 3, a(2)+1 = 5. Are there any more? Note that a(3) = 46657 = 13 * 37 * 97 is a 3-brilliant number. a(3)-5, a(3)-3 and a(3)+5 are semiprime; a(3)-7 and a(3)+7 are primes. - Jonathan Vos Post (jvospost2(AT)yahoo.com), Dec 09 2004

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Eric Weisstein's World of Mathematics, Ultrafactorial.

Cf. A002109.

Cf. A000166, A000178, A002982, A002109.

Sequence in context: A001376 A053937 A132638 this_sequence A074318 A102200 A066544

Adjacent sequences: A046879 A046880 A046881 this_sequence A046883 A046884 A046885

nonn

Camillo Lamonaca (Camillo.Lamonaca(AT)dva.gov.au)