OFFSET
1,1
COMMENTS
Primes p that there is at least one such k for which k - d(k) = p, where d(k) is the number of divisors of k (A000005).
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..7955
EXAMPLE
2 is present, as we have 6 - d(6) = 6 - 4 = 2.
3 is present, as we have 5 - d(5) = 3. The same holds for all lesser twin primes (A001359).
MATHEMATICA
lim = 10000; s = Select[Sort@ DeleteDuplicates@ Table[n - DivisorSigma[0, n], {n, lim}], PrimeQ]; Take[s, 79] (* Michael De Vlieger, Oct 13 2015 *)
PROG
(PARI)
allocatemem(123456789);
v060990 = vector(uplim1);
for(n=3, uplim1, v060990[n-numdiv(n)]++);
A060990 = n -> if(!n, 2, v060990[n]);
n=0; forprime(p=2, 131071, if((A060990(p) > 0), n++; write("b263090.txt", n, " ", p)));
(Scheme, with Antti Karttunen's IntSeq-library)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 11 2015
STATUS
approved