

A249644


Primes p such that sigma(pk) = sigma(p+k) has no solution, where sigma is A000203.


2



2, 3, 5, 7, 11, 13, 17, 29, 37, 43, 47, 59, 67, 71, 79, 89, 97, 107, 109, 127, 137, 139, 167, 181, 191, 197, 199, 211, 223, 227, 229, 251, 263, 283, 311, 331, 337, 347, 353, 389, 409, 439, 443, 449, 457, 461, 463, 467, 503, 521, 557, 587, 599, 601, 617, 619, 631, 641, 677, 683, 719
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OFFSET

1,1


COMMENTS

Primes that are not in A070299.  Franklin T. AdamsWatters, Nov 02 2014


LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..373


EXAMPLE

2 is in this sequence because sigma(21) < sigma(2+1) and 2 is prime.
23 is not in the sequence because sigma(233) = sigma(23+3) = 42.


PROG

(PARI) forprime(p=1, 10^3, c=0; for(k=1, p1, if(sigma(p+k)==sigma(pk), c++; break)); if(!c, print1(p, ", "))) \\ Derek Orr, Nov 03 2014
(PARI) is(n)=forcomposite(c=15, n1, if(sigma(c)==sigma(2*nc), return(0))); isprime(n) \\ Charles R Greathouse IV, Nov 03 2014


CROSSREFS

Cf. A000203, A070299.
Sequence in context: A152245 A007693 A174048 * A103144 A105909 A197187
Adjacent sequences: A249641 A249642 A249643 * A249645 A249646 A249647


KEYWORD

nonn


AUTHOR

JuriStepan Gerasimov, Nov 02 2014


STATUS

approved



