A068357 Duplicate of A067891.
367, 919, 30593, 95393, 117571, 124759, 147341, 197261, 334541, 344417, 463219
Offset: 1
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
7 is a member as 6 and 8 both have 4 divisors; 19 is a member as 18 and 20 both have 6 divisors each.
with(numtheory):j := 0:for i from 1 to 10000 do b := ithprime(i): if nops(divisors(b-1))=nops(divisors(b+1)) then j := j+1:a[j] := b:fi:od:seq(a[k],k=1..j);
Prime[ Select[ Range[ 700 ], Length[ Divisors[ Prime[ #1 ] - 1 ]] == Length[ Divisors[ Prime[ #1 ] + 1 ]] & ]] Select[Prime[Range[1000]],DivisorSigma[0,#-1]==DivisorSigma[0,#+1]&] (* Harvey P. Dale, Jun 08 2018 *)
is_A067889(p)=numdiv(p-1)==numdiv(p+1)&&isprime(p) \\ M. F. Hasler, Jul 31 2015
f[n_]:=Plus@@Divisors[Prime[n]-2]==Plus@@Divisors[Prime[n]+2]; lst={};Do[If[f[n],AppendTo[lst,Prime[n]]],{n,2*9!}];lst
Select[Prime@ Range[10^5], Equal @@ DivisorSigma[1, # + {-3, 3}] &] (* Giovanni Resta, May 15 2016 *)
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