This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A062700 Terms of A000203 that are prime. 18
 3, 7, 13, 31, 31, 127, 307, 1093, 1723, 2801, 3541, 8191, 5113, 8011, 10303, 19531, 17293, 28057, 30941, 30103, 131071, 88741, 86143, 147073, 524287, 292561, 459007, 492103, 797161, 552793, 579883, 598303, 684757, 704761, 732541, 735307 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sorted and duplicates removed, this gives A023195. LINKS Harry J. Smith and Chai Wah Wu, Table of n, a(n) for n = 1..10000 n=1..100 from Harry J. Smith EXAMPLE sigma(2) = 3, sigma(4) = 7, sigma(9) = 13 are the first three prime terms of A000203. Hence the sequence starts 3, 7, 13. MATHEMATICA Select[DivisorSigma[1, Range[1000000]], PrimeQ] (* Harvey P. Dale, Nov 09 2012 *) PROG (MAGMA) [ c: n in [1..1000000] | IsPrime(c) where c:=SumOfDivisors(n) ]; // Klaus Brockhaus, Oct 21 2009 (PARI) je=[]; for(n=1, 1000000, if(isprime(sigma(n)), je=concat(je, sigma(n)))); je (PARI) { n=0; for (m=1, 10^9, if(isprime(a=sigma(m)), write("b062700.txt", n++, " ", a); if (n==100, break)) ) } \\ Harry J. Smith, Aug 09 2009 (Python) from sympy import isprime, divisor_sigma A062700_list = [3]+[n for n in (divisor_sigma(d**2) for d in range(1, 10**4)) if isprime(n)] # Chai Wah Wu, Jul 23 2016 CROSSREFS Cf. A000203 (sigma(n), sum of divisors of n), A034885 (record values of sigma(n)), A023195 (prime numbers that are the sum of the divisors of some n), A100382 (record values of A062700). Sequence in context: A147098 A109291 A199218 * A249378 A136060 A023227 Adjacent sequences:  A062697 A062698 A062699 * A062701 A062702 A062703 KEYWORD nonn AUTHOR Jason Earls, Jul 11 2001 EXTENSIONS Edited by Klaus Brockhaus, Oct 21 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 26 19:44 EDT 2019. Contains 323597 sequences. (Running on oeis4.)