The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A164320 Primes p such that sums of divisors of the two adjacent integers are each > 2*p. 1
 19, 31, 41, 71, 79, 89, 101, 103, 113, 127, 139, 197, 199, 223, 271, 281, 307, 349, 353, 367, 379, 401, 439, 449, 461, 463, 491, 499, 521, 571, 607, 617, 619, 641, 643, 701, 727, 739, 761, 769, 811, 821, 859, 881, 911, 919, 929, 941, 953, 967, 991, 1039, 1061 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. C. Greubel, Table of n, a(n) for n = 1..5000 FORMULA Intersection of A164318 and A164319. EXAMPLE For p=19, the sum of the divisors of 18 is A000203(18)=39 > 2*19, and the sum of the divisors of 20 is A000203(20)= 42 > 2*19, so p=19 is in the sequence. MATHEMATICA f[n_]:=Plus@@Divisors[n]; lst={}; Do[p=Prime[n]; If[f[p-1]>2*p&&f[p+1]> 2*p, AppendTo[lst, p]], {n, 6!}]; lst Select[Prime[Range[200]], DivisorSigma[1, #-1]>2#&&DivisorSigma[ 1, #+1]>2#&] (* Harvey P. Dale, Nov 10 2011 *) CROSSREFS Cf. A164318, A164319. Sequence in context: A159043 A040088 A178251 * A154418 A120337 A120115 Adjacent sequences:  A164317 A164318 A164319 * A164321 A164322 A164323 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Aug 12 2009 EXTENSIONS References to unrelated sequences removed by R. J. Mathar, Aug 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 January 22 07:30 EST 2020. Contains 331139 sequences. (Running on oeis4.)