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
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:
MATHEMATICA
Insert[Prime[Range[60]], 4, 3] (* Harvey P. Dale, Jan 26 2024 *)
PROG
(PARI) a(n)=if(n>3, prime(n-1), n+1) \\ Charles R Greathouse IV, Aug 26 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michel Lagneau, Sep 04 2010
EXTENSIONS
Switched comment and name. Charles R Greathouse IV, Nov 04 2013
STATUS
approved