

A175787


Primes together with 4.


3



2, 3, 4, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277
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OFFSET

1,1


COMMENTS

sopf(n) is the sum of the distinct primes dividing n (A008472). Because sopf(n) = n if n is prime, this sequence is numbers n such that n^sopf(n) = sopf(n)^n.
Numbers n whose sum of prime factors is n.  Arkadiusz Wesolowski, Jan 17 2012
Numbers n such that 2n has exactly four divisors.  Wesley Ivan Hurt, Jul 01 2013
Numbers n such that n^2 does not divide n!.  Charles R Greathouse IV, Nov 04 2013
Numbers n such that n does not divide (n1)!.  Elizabeth Axoy, Sep 24 2019


LINKS

Table of n, a(n) for n=1..60.


FORMULA

a(n) = A046022(n+1).  Omar E. Pol, Nov 27 2012


MAPLE

with(numtheory): digits:=200:nn:=200:for a from 1 to nn do: t1:=ifactors(a)[2]:t2:=sum(t1[i][1], i=1..nops(t1)) :if a^t2=t2^a then printf(`%d, `, a):else fi:od:


PROG

(PARI) a(n)=if(n>3, prime(n1), n+1) \\ Charles R Greathouse IV, Aug 26 2011


CROSSREFS

Cf. A008472, A046022.
Sequence in context: A033070 A211781 A046022 * A073019 A174291 A007885
Adjacent sequences: A175784 A175785 A175786 * A175788 A175789 A175790


KEYWORD

nonn,easy


AUTHOR

Michel Lagneau, Sep 04 2010


EXTENSIONS

Switched comment and name. Charles R Greathouse IV, Nov 04 2013


STATUS

approved



