A168567 Sum of divisors (sigma(n)) of the prime's previous and next numbers.

5, 10, 19, 27, 46, 52, 70, 81, 96, 128, 135, 151, 186, 180, 196, 218, 258, 264, 270, 339, 309, 354, 350, 414, 423, 433, 426, 442, 496, 488, 567, 588, 558, 624, 638, 672, 632, 657, 732, 668, 816, 882, 868, 802, 867, 933, 954, 960, 902, 992, 996, 1176, 1143, 1196

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

a(1) = sigma(2-1) + sigma(2+1) = 1 + 4 = 5. a(3) = sigma(5-1) + sigma(5+1) = 7 + 12 = 19.

Mathematica

f[n_]:=Plus@@Divisors[n]; lst={}; Do[p=Prime[n]; AppendTo[lst, f[p-1]+f[p+1]], {n, 5!}]; lst
DivisorSigma[1, #-1]+DivisorSigma[1, #+1]&/@Prime[Range[60]] (* Harvey P. Dale, Jan 18 2019 *)

Prog

(PARI) apply(p->sigma(p-1)+sigma(p+1), primes(100)) \\ Charles R Greathouse IV, May 30 2013

Crossrefs

Cf. A000203.

Sequence in context: A030776 A115289 A358306 * A185440 A134467 A178132

Adjacent sequences: A168564 A168565 A168566 * A168568 A168569 A168570

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Nov 30 2009

Status

approved