login
A339864
Primes of the form p + sigma(p-1) for primes p.
1
3, 19, 29, 41, 59, 103, 131, 139, 151, 149, 229, 211, 269, 349, 269, 389, 439, 383, 523, 419, 449, 727, 701, 787, 569, 683, 719, 659, 991, 859, 811, 1009, 887, 1153, 877, 1109, 1489, 1489, 1223, 1327, 1657, 1579, 1259, 1693, 2221, 1409, 2011, 1607, 1831, 2251, 1867, 2503, 1801, 1811, 2677, 2689
OFFSET
1,1
COMMENTS
Terms are in order of increasing p.
Terms that occur more than once include 269, 1489, 2903, 3271, 5099, 7159.
LINKS
FORMULA
a(n) = A339862(n) + sigma(A339862(n)-1).
EXAMPLE
A339862(3) = 11 so a(3) = 11 + sigma(11-1) = 29.
MAPLE
select(isprime, map(t -> t + numtheory:-sigma(t-1), [seq(ithprime(i), i=1..200)]));
MATHEMATICA
Select[#+DivisorSigma[1, #-1]&/@Prime[Range[200]], PrimeQ] (* Harvey P. Dale, Jan 31 2021 *)
CROSSREFS
Sequence in context: A295322 A296934 A062619 * A180451 A108137 A250027
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Dec 19 2020
EXTENSIONS
Definition clarified by Harvey P. Dale, Jan 31 2021
STATUS
approved