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
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, May 17 2011
STATUS
approved