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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A190722 Primes p such that A008472(p-1) = A008472(p+1) and is a prime. 2
 3, 45751, 149351, 171529, 223099, 434237, 678077, 706841, 1996297, 3993037, 6340457, 7199113, 7419761, 9000317, 13129271, 15052777, 17193217, 18436879, 18749881, 18998519, 23353469, 23689423, 33746663, 40985411, 41437751, 43547797, 51198097, 53773651, 56825687, 60207809, 62190113, 79778899, 81708353, 83019421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A008472 is the sum of the distinct primes dividing n. LINKS Amiram Eldar, Table of n, a(n) for n = 1..223 (calculated from the b-file at A203182) EXAMPLE For p = 45751, p-1 = 2*3*5^3*61; 2+3+5+61=71 and p+1 = 2^3*7*19*43; 2+7+19+43 = 71. MATHEMATICA fQ[n_] := Block[{pn = Plus @@ (First@# & /@ FactorInteger[n - 1]), pp = Plus@@ (First@# & /@ FactorInteger[n + 1])}, pn == pp && PrimeQ[pn]]; p = 2; lst = {}; While[p < 10^8, If[fQ@p, AppendTo[lst, p]; Print@p]; p = NextPrime@p]; lst pQ[n_]:=Module[{p1=Total[FactorInteger[n-1][[All, 1]]], p2=Total[ FactorInteger[ n+1][[All, 1]]]}, p1==p2&&PrimeQ[p1]]; Select[ Prime[ Range[5*10^6]], pQ] (* Harvey P. Dale, Jun 18 2017 *) PROG (MAGMA) [p:p in PrimesInInterval(3, 10^8)|(&+PrimeDivisors(p-1) eq &+PrimeDivisors(p+1)) and IsPrime(&+PrimeDivisors(p-1))]; // Marius A. Burtea, Nov 14 2019 CROSSREFS Cf. A190680, A008472, A086711. Subsequence of A203182. Sequence in context: A135760 A003541 A086829 * A171365 A115976 A340182 Adjacent sequences:  A190719 A190720 A190721 * A190723 A190724 A190725 KEYWORD nonn AUTHOR Robert G. Wilson v, May 17 2011 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 December 3 05:05 EST 2021. Contains 349445 sequences. (Running on oeis4.)