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A212483 Smallest number k such that the sum of the distinct prime divisors of k equals n times a prime. 1
2, 21, 14, 15, 21, 35, 33, 39, 65, 51, 57, 95, 69, 115, 86, 87, 93, 155, 217, 111, 122, 123, 129, 215, 141, 235, 158, 159, 265, 371, 177, 183, 194, 427, 201, 335, 213, 219, 365, 511, 237, 395, 249, 415, 446, 267, 278, 623, 1246, 291, 302, 303, 309, 515, 321 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Smallest k such that sopf(k) = n*p, p prime.
LINKS
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
Sequence in context: A072397 A077208 A321534 * A084313 A140268 A106422
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 02 2012
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)