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 A139171 a(n) = smallest prime number p such that p!/n is an integer. 3
 2, 2, 3, 5, 5, 3, 7, 5, 7, 5, 11, 5, 13, 7, 5, 7, 17, 7, 19, 5, 7, 11, 23, 5, 11, 13, 11, 7, 29, 5, 31, 11, 11, 17, 7, 7, 37, 19, 13, 5, 41, 7, 43, 11, 7, 23, 47, 7, 17, 11, 17, 13, 53, 11, 11, 7, 19, 29, 59, 5, 61, 31, 7, 11, 13, 11, 67, 17, 23, 7, 71, 7, 73, 37, 11, 19, 11, 13, 79, 7, 11 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 Wikipedia, Legendre's formula MAPLE f:= proc(n) local F, m, Q, E, p; F:= ifactors(n)[2]; m:= nops(F); Q:= map(t -> t[1], F); E:= map(t -> t[2], F); p:= max(Q)-1; do p:= nextprime(p); if andmap(i -> add(floor(p/Q[i]^j), j=1..floor(log[Q[i]](p))) >= E[i], [\$1..m]) then return p fi; od end proc: f(1):= 2: map(f, [\$1..100]); # Robert Israel, Mar 07 2018 MATHEMATICA a = {}; Do[m = 1; While[ ! IntegerQ[Prime[m]!/n], m++ ]; AppendTo[a, Prime[m]], {n, 1, 100}]; a PROG (PARI) a(n) = forprime(p=2, , if (!(p! % n), return (p))); \\ Michel Marcus, Mar 08 2018 CROSSREFS Prime equivalent of Kempner numbers A002034. For quotients p!/n see A139170. For indices of primes in this sequence see A139169. Cf. A082672, A089085, A089130, A117141, A007749, A139056-A139066, A139068, A137390, A139070-A139075, A139148-A139157, A139159, A139160-A139166, A139089, A139168-A139170. Sequence in context: A323480 A330404 A340575 * A329570 A279724 A050174 Adjacent sequences: A139168 A139169 A139170 * A139172 A139173 A139174 KEYWORD nonn,look AUTHOR Artur Jasinski, Apr 11 2008 STATUS approved

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Last modified November 29 17:22 EST 2023. Contains 367445 sequences. (Running on oeis4.)