A249644 Primes p such that sigma(p-k) = sigma(p+k) has no solution, where sigma is A000203.

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

Offset

1,1

Comments

Primes that are not in A070299. - Franklin T. Adams-Watters, 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(2-1) < sigma(2+1) and 2 is prime.
23 is not in the sequence because sigma(23-3) = sigma(23+3) = 42.

Prog

(PARI) forprime(p=1, 10^3, c=0; for(k=1, p-1, if(sigma(p+k)==sigma(p-k), c++; break)); if(!c, print1(p, ", "))) \\ Derek Orr, Nov 03 2014
(PARI) is(n)=forcomposite(c=15, n-1, if(sigma(c)==sigma(2*n-c), 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

Juri-Stepan Gerasimov, Nov 02 2014

Status

approved