A099497 -id:A099497 - cp's OEIS frontend

A099498 Semiprimes of the form A007925(n) = n^(n+1)-(n+1)^n.

7849, 3667649, 91171007, 2395420006033, 11877172892329028459041, 604107995057426434824791, 107174878415004743976428761769, 424678439961073471604787362241217, 1983672219242345491970468171243171249, 10788746499945827829225142589096882612369, 42855626937384013751014398588294858582343260060671

Offset: 1

Hugo Pfoertner, Oct 19 2004

nonn

			a(1)=7849 because 5^6-6^5=7849=47*167 is a semiprime.

Cf. A007925 n^(n+1)-(n+1)^n, A072179 n^(n+1)-(n+1)^n is prime, A099499 primes of the form n^(n+1)-(n+1)^n, A099497 n^(n+1)-(n+1)^n is a semiprime.

IsSemiprime:=func; [s: n in [3..30] | IsSemiprime(s) where s is n^(n+1)-(n+1)^n]; // Vincenzo Librandi, Sep 21 2012

Select[Table[n^(n + 1) - (n + 1)^n, {n, 30}], PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 21 2012 *)

a(9)-a(11) from Vincenzo Librandi, Sep 21 2012

A099499 Primes of the form A007925(n)=n^(n+1)-(n+1)^n.

Original entry on oeis.org

17, 162287, 2486784401, 83695120256591, 84721522804414816904952398305908708011513455440403306207160333176150520399

Offset: 1

Hugo Pfoertner, Oct 19 2004

nonn

The next term a(6)=883^884-884^883 has 2605 decimal digits and is too large to display.

			a(2)=162287 because A007925(A072179(2))=6^7-7^6=162287 is prime.

Cf. A007925 n^(n+1)-(n+1)^n, A072179 n^(n+1)-(n+1)^n is prime, A099497 n^(n+1)-(n+1)^n is a semiprime, A099498 semiprimes of the form n^(n+1)-(n+1)^n.

[a: n in [0..50] | IsPrime(a) where a is n^(n+1)-(n+1)^n ]; // Vincenzo Librandi, Jul 18 2012

Select[Table[n^(n+1)-(n+1)^n,{n,0,1000}],PrimeQ] (* Vincenzo Librandi, Jul 18 2012 *)

cp's OEIS Frontend

A099498 Semiprimes of the form A007925(n) = n^(n+1)-(n+1)^n.

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