A055813 Primes arising in A064205.

2, 5, 19, 263, 373, 1033, 65551, 123833, 283553, 292993, 2197633, 5778673, 12795193, 10500613, 19980283, 32213033, 36978853, 72494813, 140724953, 164119063, 183105509, 193710277, 320210941, 450065801, 268354393, 496922891, 506906473, 1333406021

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..5000 (terms 1..276 from Michel Marcus)

Formula

a(n) = A007503(A064205(n)). - Amiram Eldar, Dec 06 2022

Example

a(3) = 19 since, for A064205(3) = 8, sigma(8)+tau(8) = 15+4 = 19, a prime number. - Michael De Vlieger, Dec 17 2016

Mathematica

Select[Table[Total@ Map[DivisorSigma[#, n] &, {0, 1}], {n, 10^7}], PrimeQ] (* Michael De Vlieger, Dec 17 2016 *)

Prog

(PARI) lista(nn) = for (n=1, nn, if (isprime(p=sigma(n) + numdiv(n)), print1(p, ", "))); \\ Michel Marcus, Dec 18 2016

Crossrefs

Cf. A007503, A064205.

Sequence in context: A359116 A080280 A218386 * A119550 A119563 A270398

Adjacent sequences: A055810 A055811 A055812 * A055814 A055815 A055816

Keyword

nonn

Author

Labos Elemer, Nov 22 2001

Status

approved