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A229269
Numbers n for which n-n' is prime, n' being the arithmetic derivative of n.
4
3, 9, 10, 14, 15, 21, 26, 33, 35, 38, 39, 50, 51, 62, 65, 66, 69, 70, 77, 78, 86, 91, 93, 95, 102, 110, 111, 114, 122, 123, 129, 130, 133, 138, 146, 154, 159, 161, 170, 174, 190, 201, 203, 206, 209, 213, 215, 217, 218, 221, 222, 230, 238, 249, 258, 278, 282, 287
OFFSET
1,1
LINKS
EXAMPLE
15 is in the list because 15ā€™ = 8 and 15 - 8 = 7 that is prime.
MAPLE
with(numtheory); P:=proc(q) local a, n, p; for n from 1 to q do
a:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]); if isprime(n-a) then print(n); fi; od; end: P(10^5);
PROG
(Python)
from sympy import isprime, factorint
A229269 = [n for n in range(1, 10**4) if isprime(n-sum([int(n*e/p) for p, e in factorint(n).items()]))] # Chai Wah Wu, Aug 21 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Sep 18 2013
STATUS
approved