OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)
Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).
FORMULA
If A066075(m) = 1, then prime(m) is a term.
MATHEMATICA
With[{s = KeySort@ PositionIndex@ Array[DivisorSigma[1, #] - 1 &, 10^5]}, Take[#, 51] &@ Keys@ KeySelect[s, PrimeQ@ # && Length@ Lookup[s, #] == 1 &]] (* Michael De Vlieger, Jul 16 2017 *)
PROG
(PARI) { n=0; for (m=1, 10^9, p=prime(m); a=1; for (x=1, p - 1, if (p == (sigma(x) - 1), a++; break)); if (a==1, write("b066076.txt", n++, " ", p); if (n==1000, return)) ) } \\ Harry J. Smith, Nov 10 2009
(PARI) is(n) = isprime(n) && invsigmaNum(n + 1) == 1; \\ Amiram Eldar, Aug 18 2024, using Max Alekseyev's invphi.gp
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 03 2001
STATUS
approved