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

1,1

Links

Table of n, a(n) for n=1..11.

Example

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

Mathematica

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

Prog

(Magma) IsSemiprime:=func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [3..30] | IsSemiprime(s) where s is n^(n+1)-(n+1)^n]; // Vincenzo Librandi, Sep 21 2012

Crossrefs

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.

Sequence in context: A234477 A286181 A045277 * A286208 A268583 A045292

Adjacent sequences: A099495 A099496 A099497 * A099499 A099500 A099501

Keyword

nonn

Author

Hugo Pfoertner, Oct 19 2004

Extensions

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

Status

approved