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A175787
Primes together with 4.
5
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
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
Sequence in context: A211781 A348283 A046022 * A345899 A073019 A174291
KEYWORD
nonn,easy
AUTHOR
Michel Lagneau, Sep 04 2010
EXTENSIONS
Switched comment and name. Charles R Greathouse IV, Nov 04 2013
STATUS
approved