A226959 a(0)=1 and a(n)=prime(n)*lcm(prime(n)-1, a(n-1)) for n > 0.

1, 2, 6, 60, 420, 4620, 60060, 4084080, 232792560, 5354228880, 155272637520, 4813451763120, 178097715235440, 7302006324653040, 313986271960080720, 14757354782123793840, 782139803452561073520, 46146248403701103337680, 2814921152625767303598480

Offset: 0

Author

José María Grau Ribas, Jun 24 2013

Keywords

• nonn

Comments

A226957(a(n)) = n.

Is this a subset of A168264? - Ralf Stephan, Jul 04 2013

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 0..347

Crossrefs

Cf. A226957, A002110.

Programs

Mathematica

a[0]=1; a[n_]:= a[n]=Prime[n]*LCM[a[n - 1],Prime[n] -1];
Table[a[i], {i, 1, 18}]

PARI

a(n)=if(n,my(v=primes(n),e=vector(n,i,1),f,j); forprime(p=2,v[n], f=factor(p-1); for(i=1,#f~,if(f[i,2]>1,j=primepi(f[i,1]);e[j]=max(e[j],f[i,2])))); prod(i=1,n,v[i]^e[i]),1) \\ Charles R Greathouse IV, Jun 28 2013