OFFSET
1,1
COMMENTS
Smallest k such that sopf(k) = n*p, p prime.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..5000
EXAMPLE
a(5) = 21 because 21 = 3*7 and 3 + 7 = 10 = 5*2 where 2 is prime.
MAPLE
with (numtheory):
sopf:= proc(n) option remember;
add(i, i=factorset(n))
end:
a:= proc(n) local k, p;
for k from 2 while irem(sopf(k), n, 'p')>0 or
not isprime(p) do od; k
end:
seq (a(n), n=1..100); # Alois P. Heinz, Jun 03 2012
MATHEMATICA
snk[n_]:=Module[{k=1}, While[!PrimeQ[(Total[Transpose[ FactorInteger[k]] [[1]]])/n], k++]; k]; Array[snk, 60] (* Harvey P. Dale, Jun 24 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 02 2012
STATUS
approved