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A079448
Primes p such that there is at least one integer x satisfying p=x*tau(x)-1 where tau(x)=A000005(x), the number of divisors of x.
1
3, 5, 11, 13, 23, 31, 37, 59, 61, 71, 73, 79, 83, 103, 107, 131, 139, 151, 157, 167, 191, 193, 227, 239, 263, 269, 277, 307, 311, 313, 347, 379, 397, 421, 431, 443, 449, 457, 479, 487, 491, 499, 541, 563, 571, 587, 593, 613, 619, 631, 643, 661, 673, 701, 719
OFFSET
1,1
EXAMPLE
6*tau(6)=24 hence 23 is in the sequence.
PROG
(PARI) lista(nn) = {forprime(p=2, nn, for (n=1, p, if (n*numdiv(n)-1 == p, print1(p, ", "); break; ); ); ); } \\ Michel Marcus, Dec 01 2013
CROSSREFS
Cf. A079449.
Sequence in context: A078971 A266723 A129096 * A045407 A317309 A243897
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jan 13 2003
STATUS
approved